Hello Andy,
Frankly, we don't think the problem is related to any Telerik control. We made a
quick search on Google and found some related posts that might help you solve
your
issue.
http://forums.asp.net/p/1390221/2968593.aspx
http://www.sitepoint.com/forums/showthread.php?t=492036
http://www.itags.org/dotnet/252513/
I
hope that helps.
Regards,
Paul
the Telerik team