Linq and timeout

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Been having a weird issue for the past few months -- might have started when
I moved my asp.net application to framework 3.5 so I could start using Linq
to Sql. When I open my application in VS2008 and click run, it ALWAYS
returns back to me in about 30 seconds saying there was a timeout in the
first bit of Linq that was executed. If I press "restart", to try running
the application again, it ALWAYS works the second time, and will continue to
work unless I wait about 15 or 30 minutes between runs. Then I'm back to the
timeout again on first connection. The sql server is on another box on the
same network, and I can assure you, there are no connectivity issues getting
to it. Feels like some sort of "connection pool" timeout, but I'm guessing.
Any ideas?

Thanks for the help!