The problem: your data has ampersands (&) in it, but you must submit it as a query string to your asp dot net app. After you have sent it, however, the string is truncated at the & character.
The solution: HttpUtility.URLEncode/.URLDecode to send query strings that contain ampersands as data.
The story:
A coworker reported a strange bug in an app that I am troubleshooting. Sometimes the process would work; sometimes it wouldn't. The first suspect was my code, so I looked through it. My first find was that string variable was being truncated for some mysterious reason. So I suspected that there may be faulty data that was feeding the drop down menu. After looking at the data, I found that there was no such problems. However, I did find an old friend of mine: the ampersand.
About a week or two ago I had to fix a bug where the ampersand was braking an xml feed. In that case I was able to substitute in the data the & character for an and. In the new app, I couldn't do that.
I first tried to encode the string in html. This didn't work. Looking at the string that it output, I found the problem: the encoding contained... and ampersand!
I googled again. This time, I found the solution in the link below: encode to URLEncoding, and this will substitute the & with something that doesn't use it.
Source that gave the answer:
http://discuss.joelonsoftware.com/default.asp?dotnet.12.414245.11