Boolean parsing exception - WebControls.BitmapViewer

Been using using GraphicsMill.Net 3.1 for 6 months now inside a web site. The site has been under increasing load and as of the past few weeks, the error below comes up with increasing frequency. There are many pages on the site, but only pages with BitmapViewer controls throw this exception. Wondering if this is a known issue or if you can point me in the right direction to solving the problem.

Environment:
-GraphicsMill.Net 3.1
-IIS 6
-ASP.Net 2.0

Process information:
Process ID: 1676
Process name: w3wp.exe
Account name: NT AUTHORITY\NETWORK SERVICE

Exception information:
Exception type: FormatException
Exception message: String was not recognized as a valid Boolean.

Request information:
Request URL:
Request path:
User host address:
User:
Is authenticated: False
Authentication Type:
Thread account name: NT AUTHORITY\NETWORK SERVICE

Thread information:
Thread ID: 7
Thread account name: NT AUTHORITY\NETWORK SERVICE
Is impersonating: False
Stack trace: at System.Boolean.Parse(String value)
at Aurigma.GraphicsMill.WebControls.BitmapViewer.System.Web.UI.IPostBackDataHandler.LoadPostData(String postDataKey, NameValueCollection postCollection)
at System.Web.UI.Page.ProcessPostData(NameValueCollection postData, Boolean fBeforeLoad)
at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

So far, after 1 day of running 3.5, we have not seen this error. Will have to give it more time to be sure since we did not know how to reproduce it. I'll give it a week and let you know if the problem is resolved.

-Grady