this is all in you ASP.Net page ?
var q = from p in PData.Customers
select p.Custom_ID;
if (q.Count() != 0)
{
:.
}
maybe this is a memory leak!try to limit source code for centralizing problem & monitor your PC memory.
shutdown Server SQL and restart.
also try to use manually Connection.Open()/Close/()Connection.BeginTransaction/... (for testing)