Vitaly,
I am using cookies. That's what I said - here are my IIS logs - let me know if you think you understand what the problem is: you will see that I am passing the AuthCookie : The application is written in ASP.Net MVC 4 :
<a href="aurup:?uploadUrl=http://mobile.assemblyline.carponents.com/mygarage/AurigmaUpload&redirectUrl=http://mobile.assemblyline.carponents.com/mygarage/AurigmaUpload&redirectDelay=60&returnUrl=../mygarage/AurigmaUpload&uploadTimeOut=1000&licenseKey=79FF1-000DF-6C830-00008-9BC01-B46D2F&minimumVersion=1.4&cookies=AuthCookie=@Model.AuthCookie"> Upload Photos</a>
IIS 8.0 logs :
2013-05-06 22:45:05 10.242.51.212 POST /Account/Login ReturnUrl=/mygarage/aurigmaupload 80 1 69.119.185.96 Mozilla/5.0+(Macintosh;+Intel+Mac+OS+X+10.6;+rv:20.0)+Gecko/20100101+Firefox/20.0 fbm_447175668666391=base_domain=.carponents.com;+__utma=185561659.853594019.1349941699.1367802103.1367864018.604;+__utmz=185561659.1366383199.568.15.utmcsr=meetup.com|utmccn=(referral)|utmcmd=referral|utmcct=/Jersey-Shore-Tech/members/82543032/;+__utmc=185561659;+AuthCookie=EE89A3C5FE0096905639240B665C1FAE21D0EAA31739FF06E6B1B2878C67864247B4B9022145CA521CB81EE921A401415ECC0D2038FCE93202220B7B20897C2FD08D9BC7
http://mobile.assemblyli...=/mygarage/aurigmaupload 302 0 0 8954
2013-05-06 22:45:05 10.242.51.212 GET /mygarage/aurigmaupload - 80 1 69.119.185.96 Mozilla/5.0+(Macintosh;+Intel+Mac+OS+X+10.6;+rv:20.0)+Gecko/20100101+Firefox/20.0 fbm_447175668666391=base_domain=.carponents.com;+__utma=185561659.853594019.1349941699.1367802103.1367864018.604;+__utmz=185561659.1366383199.568.15.utmcsr=meetup.com|utmccn=(referral)|utmcmd=referral|utmcct=/Jersey-Shore-Tech/members/82543032/;+__utmc=185561659;+AuthCookie=E033B35056BD250892CED4ABABC3A467B12383EE7C634A9FD340458C02E5F9082B23E85D1915E8F6B85F8C3621CB90812753AB71E2FA51E3B8BCE6F0D4032310AB9A17E3
http://mobile.assemblyli...=/mygarage/aurigmaupload 200 0 0 177
2013-05-06 22:51:47 10.242.51.212 GET /mygarage/aurigmaupload - 80 - 198.228.201.146 Mozilla/5.0+(Linux;+U;+Android+4.1.1;+en-us;+SAMSUNG-SGH-I747+Build/JRO03L)+AppleWebKit/534.30+(KHTML,+like+Gecko)+Version/4.0+Mobile+Safari/534.30 __utma=185561659.463560503.1365093772.1365788687.1366389486.6;+__utmz=185561659.1365093772.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none);+AuthCookie= - 302 0 0 15
2013-05-06 22:51:47 10.242.51.212 GET /Account/Login ReturnUrl=%2fmygarage%2faurigmaupload 80 - 198.228.201.146 Mozilla/5.0+(Linux;+U;+Android+4.1.1;+en-us;+SAMSUNG-SGH-I747+Build/JRO03L)+AppleWebKit/534.30+(KHTML,+like+Gecko)+Version/4.0+Mobile+Safari/534.30 __utma=185561659.463560503.1365093772.1365788687.1366389486.6;+__utmz=185561659.1365093772.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none);+AuthCookie= - 200 0 0 31
2013-05-06 22:51:52 10.242.51.212 POST /Account/Login ReturnUrl=%2fmygarage%2faurigmaupload 80 - 198.228.201.146 Mozilla/5.0+(Linux;+U;+Android+4.1.1;+en-us;+SAMSUNG-SGH-I747+Build/JRO03L)+AppleWebKit/534.30+(KHTML,+like+Gecko)+Version/4.0+Mobile+Safari/534.30 __utma=185561659.463560503.1365093772.1365788687.1366389486.6;+__utmz=185561659.1365093772.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none);+AuthCookie=
http://mobile.assemblyli...mygarage%2faurigmaupload 302 0 0 452
2013-05-06 22:51:52 10.242.51.212 GET /mygarage/aurigmaupload - 80 15 198.228.201.146 Mozilla/5.0+(Linux;+U;+Android+4.1.1;+en-us;+SAMSUNG-SGH-I747+Build/JRO03L)+AppleWebKit/534.30+(KHTML,+like+Gecko)+Version/4.0+Mobile+Safari/534.30 __utma=185561659.463560503.1365093772.1365788687.1366389486.6;+__utmz=185561659.1365093772.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none);+AuthCookie=130EA9D149EC82D43B9C4D7B552C5F4411C78131AEF953698D29A887D76EAFE15D90936A40D9F69F2050F56A48C47C94D4EB6CE12DD9155642A536792D23BF55F329E8A2
http://mobile.assemblyli...mygarage%2faurigmaupload 200 0 0 46
2013-05-06 22:52:19 10.242.51.212 POST /mygarage/AurigmaUpload - 80 15 198.228.201.146 Aurigma+Up AuthCookie=130EA9D149EC82D43B9C4D7B552C5F4411C78131AEF953698D29A887D76EAFE15D90936A40D9F69F2050F56A48C47C94D4EB6CE12DD9155642A536792D23BF55F329E8A2 - 500 0 0 2293
2013-05-06 22:53:11 10.242.51.212 GET /Account/Login ReturnUrl=%2fmygarage%2fAurigmaUpload 80 - 100.1.88.2 Mozilla/5.0+(iPhone;+CPU+iPhone+OS+6_0_1+like+Mac+OS+X)+AppleWebKit/536.26+(KHTML,+like+Gecko)+Version/6.0+Mobile/10A523+Safari/8536.25 AuthCookie
+__utma=185561659.860825231.1365538111.1365540505.1366389776.3;+__utmz=185561659.1365538111.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none) - 200 0 0 31
2013-05-06 22:53:25 10.242.51.212 POST /Account/Login ReturnUrl=%2fmygarage%2fAurigmaUpload 80 - 100.1.88.2 Mozilla/5.0+(iPhone;+CPU+iPhone+OS+6_0_1+like+Mac+OS+X)+AppleWebKit/536.26+(KHTML,+like+Gecko)+Version/6.0+Mobile/10A523+Safari/8536.25 AuthCookie
+__utma=185561659.860825231.1365538111.1365540505.1366389776.3;+__utmz=185561659.1365538111.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)
http://mobile.assemblyli...mygarage%2fAurigmaUpload 302 0 0 62
2013-05-06 22:53:25 10.242.51.212 GET /mygarage/AurigmaUpload - 80 15 100.1.88.2 Mozilla/5.0+(iPhone;+CPU+iPhone+OS+6_0_1+like+Mac+OS+X)+AppleWebKit/536.26+(KHTML,+like+Gecko)+Version/6.0+Mobile/10A523+Safari/8536.25 AuthCookie=FB8C1DC14854248E23C6CBACA59012E8C6CB477C90FEC31CD151FDF4FAF09011AFDD75D6B978EF06AAE909F598F7186DD597E8BED30C1A11970F91B71C5A14EEC245DD64;+__utma=185561659.860825231.1365538111.1365540505.1366389776.3;+__utmz=185561659.1365538111.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none)
http://mobile.assemblyli...mygarage%2fAurigmaUpload 200 0 0 62
2013-05-06 22:53:56 10.242.51.212 POST /mygarage/AurigmaUpload - 80 15 100.1.88.2 Aurigma+Up+1.7.5+(iPhone;+iPhone+OS+6.0.1;+en_US) AuthCookie=FB8C1DC14854248E23C6CBACA59012E8C6CB477C90FEC31CD151FDF4FAF09011AFDD75D6B978EF06AAE909F598F7186DD597E8BED30C1A11970F91B71C5A14EEC245DD64 - 500 0 0 3447