I'm not aware of any patch problems. Presumably you must have a set of base statistics upon which to base this ?
Things to look for :-
processes running that shouldn't - msi installer perhaps?
excessive handles on the sql or agent service
fragmentation of the o/s
other external changes such as disk caching / maintainence tasks such as net backups, registry backups, changes to server memory.
Database stats out of date - can seriously slow the server down
database fragmentation - have you rebuilt any fragmented indexes
disks short of space <25% free space isn't too good.
you don't give much info on your set up so it's tricky to make better suggestions < grin >
[font="Comic Sans MS"]The GrumpyOldDBA[/font]
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http://sqlblogcasts.com/blogs/grumpyolddba/