Hi Aurigma, 
We have discovered a memory leak somewhere inside of Graphics Mill. We tracked it down using Debug Diagnostics and dumping memory after monitoring for a leak for 1 hour. In that one hour, we had a leak of 36MB. 
Here's information from the DebugDiag report. (I emailed the report to Dimitri)
WARNING - DebugDiag was not able to locate debug symbols for Aurigma.GraphicsMill.DLL, so the reported function name(s) may not be accurate.
Aurigma.GraphicsMill.DLL is responsible for 36.98 MBytes worth of outstanding allocations. The following are the top 2 memory consuming functions:
Aurigma_GraphicsMill+12b50a: 36.63 MBytes worth of outstanding allocations.Aurigma_GraphicsMill+9a3ce: 353.22 KBytes worth of outstanding allocations.
Here's a sample method call for that instruction
Function   Source   Destination 
Aurigma_GraphicsMill+9a3ce      ole32!CoTaskMemAlloc 
0x79E8EFA6       
System.StringComparer.GetHashCode(System.Object)       
System.Web.HttpApplication.System.Web.IHttpAsyncHandler.BeginProcessRequest(System.Web.HttpContext, System.AsyncCallback, System.Object)       
0x79F35EE8       
webengine!HashtableIUnknown::AddCallback+a       
webengine!HttpCompletion::ProcessRequestInManagedCode+1a9       
webengine!HttpCompletion::ProcessRequestInManagedCode+1a9       
webengine!HttpCompletion::ProcessCompletion+41      webengine!HttpCompletion::ProcessRequestInManagedCode 
webengine!CorThreadPoolWorkitemCallback+18       
0x79F8B7A5       
0x79ED8E36       
ntdll!bsearch+42       
ntdll!RtlEncodeSystemPointer+45b       
kernel32!GetModuleHandleForUnicodeString+20       
kernel32!GetModuleHandleForUnicodeString+20       
kernel32!BasepGetModuleHandleExW+17f      kernel32!GetModuleHandleForUnicodeString 
kernel32!BasepGetModuleHandleExW+23c       
ntdll!LdrpGetProcedureAddress+b3       
ntdll!LdrpCallInitRoutine+14       
ntdll!NtTestAlert+c       
ntdll!NtContinue+c       
ntdll!KiUserApcDispatcher+3a      ntdll!NtContinue 
kernel32!BaseThreadStart+34 
Here's another sample call stack
Function   Source   Destination 
Aurigma_GraphicsMill+9a3ce      ole32!CoTaskMemAlloc 
Aurigma_GraphicsMill+afaf2       
Aurigma.GraphicsMill.Color.ConvertColorSpace(Aurigma.GraphicsMill.ColorSpace)       
ntdll!ZwReleaseMutant+c       
Aurigma.GraphicsMill.Transforms.Transparentize.ThreadProc()       
Aurigma.GraphicsMill.Thread.TimerEventProcessor()      0x1EFCAA3C 
ntdll!ZwReleaseMutant+c       
Aurigma.GraphicsMill.SyncHandler.ThreadProcHandler()       
Aurigma.GraphicsMill.Thread.EntryPoint()       
Aurigma.GraphicsMill.Thread.Start()      Aurigma.GraphicsMill.Thread.EntryPoint() 
Aurigma.GraphicsMill.Transforms.BitmapTransform.ApplyTransform(Aurigma.GraphicsMill.Bitmap)      Aurigma.GraphicsMill.Thread.Start() 
CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.AddWaterMark(Aurigma.GraphicsMill.Codecs.LosslessJpegTransform, Int32, Int32)       
CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImage(System.IO.MemoryStream, Int32, Int32, Costar.Shared.Utility.PrintQuality, Boolean, Costar.Shared.Utility.AttachmentSize)      CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.AddWaterMark(Aurigma.GraphicsMill.Codecs.LosslessJpegTransform, Int32, Int32) 
CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImageFromPath(CoStar.AttachmentUtils.CoStarAurigmaImage ByRef, System.String, Int32, Int32, Costar.Shared.Utility.PrintQuality, Boolean, Boolean, Costar.Shared.Utility.AttachmentSize)      CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImage(System.IO.MemoryStream, Int32, Int32, Costar.Shared.Utility.PrintQuality, Boolean, Costar.Shared.Utility.AttachmentSize) 
CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImage(Int32, Int32, Int32, Costar.Shared.Utility.PrintQuality, Boolean, Boolean, Costar.Shared.Utility.AttachmentSize)      CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImageFromPath(CoStar.AttachmentUtils.CoStarAurigmaImage ByRef, System.String, Int32, Int32, Costar.Shared.Utility.PrintQuality, Boolean, Boolean, Costar.Shared.Utility.AttachmentSize) 
CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImage(CoStar.AttachmentUtils.ImageRequest)      CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImage(Int32, Int32, Int32, Costar.Shared.Utility.PrintQuality, Boolean, Boolean, Costar.Shared.Utility.AttachmentSize) 
Costar.AttachmentHandler.AttachmentHandler.ProcessImageRequest(System.String, System.Collections.Specialized.NameValueCollection, System.String, System.String ByRef)      CoStar.AttachmentUtils.BLAurigmaAttachmentUtils.GetCoStarImage(CoStar.AttachmentUtils.ImageRequest) 
Costar.AttachmentHandler.AttachmentHandler.ProcessRequest(System.Web.HttpContext)      Costar.AttachmentHandler.AttachmentHandler.ProcessImageRequest(System.String, System.Collections.Specialized.NameValueCollection, System.String, System.String ByRef) 
System.Web.HttpApplication.System.Web.IHttpAsyncHandler.BeginProcessRequest(System.Web.HttpContext, System.AsyncCallback, System.Object)       
0x79F35EE8       
webengine!HashtableIUnknown::AddCallback+a       
webengine!HttpCompletion::ProcessRequestInManagedCode+1a9       
webengine!HttpCompletion::ProcessRequestInManagedCode+1a9       
webengine!HttpCompletion::ProcessCompletion+41      webengine!HttpCompletion::ProcessRequestInManagedCode 
webengine!CorThreadPoolWorkitemCallback+18       
0x79F8B7A5       
0x79ED8E36       
ntdll!bsearch+42       
ntdll!RtlEncodeSystemPointer+45b       
kernel32!GetModuleHandleForUnicodeString+20       
kernel32!GetModuleHandleForUnicodeString+20       
kernel32!BasepGetModuleHandleExW+17f      kernel32!GetModuleHandleForUnicodeString 
kernel32!BasepGetModuleHandleExW+23c       
ntdll!LdrpGetProcedureAddress+b3       
ntdll!LdrpCallInitRoutine+14       
ntdll!NtTestAlert+c       
ntdll!NtContinue+c       
ntdll!KiUserApcDispatcher+3a 
We'd like to look at it closer, but we need Graphic Mills' 4.5.23 PDBs to examine the actual calls.
This is causing us to reboot production servers nightly. This is a high priority for us.
Thx, Joel