Updates to updares mess my performance

This happens to me nearly every time there is an update. I get a huge jump in preformance--the initial 1.9 (blah blah)-- I was even getting Framrates of up to 40. My usual framerates have been under 10 since 1.6 or so (except on the first day or so of an update).
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Then.. as soon as an update to the update is realeased.. my performance drops and drops. Even rolling updates cause me to get worse and worse.

I do uninstall each time... but that does not seem to matter much.

Since this happens EVERY TIME, is there some explanation a Linden could give me for this?

Pretty bizarre sounding; more details would be welcome as client framerate can differ greatly depending on the context you're in. Moved to Technical Issues for further discussion, as SL Answers is not the right place; please also contact support for further help.