Ensure that sites and webs are closed by calling their close method whenever you complete OM operations against MOSS.  Otherwise, you may see MOSS log the following:

Potentially excessive number of SPRequest objects (number) created on thread number. 

Once done with all the objects that hang off the SPSite or SPWeb, close them.

Here is a great link sent to me by a colleague describing the issue:

http://msdn2.microsoft.com/en-us/library/ms778813.aspx