http://social.msdn.microsoft.com/Forums/en-US/sqlnetfx/thread/942fe3d4-141a-486a-afdf-53f079d3a4d3

This is an issue that is new in SQL Server 2005, and is only exposed under specific conditions – namely,

the use of the x64 version of SQL...

This is an issue that is new in SQL Server 2005, and is only exposed under specific conditions – namely,

the use of the x64 version of SQL Server 2005...

I too observed similar behavior in our production servers, in SQL 2005&2008 environments.

Here is an issue that is new in SQL Server 2005, and is only exposed under specific...

U can use

DBCC FREEPOCCACHE Command to clear them regularly or

create a job that will do late in the night

for more info refer http://msdn2.microsoft.com/en-us/library/ms174283.aspx