Check for single use plans.
Plan cache, adhoc workloads and clearing the single-use plan cache bloat by Kim Tripp
I had to implement a variation of one of the queries in the post to clear ad hoc plans on a 2005 instance because the proc cache was using a very high % in the buffer pool and it started to affect performance after the instance was up for a while and usage upticked.
There are no special teachers of virtue, because virtue is taught by the whole community.
--Plato