Strange - severe WindowServer slowdowns after Safari use

Question

I've run across this really strange problem only in the past few days after years of flawless Safari performance. My symptom is apparently that WindowServer (which controls drawing to all windows onscreen and offscreen in OS X) starts taking inordinate time for even simple graphics operations after certain conditions occur in Safari. The condition seems to be permanent until I log out or restart, at which time performance returns to normal.
I first noticed this problem after starting to view TV show episodes at nbc.com (Heroes, if that makes a difference). After a few minutes, or as little as one minute, the video framerate would reduce considerably and the system as a whole became less responsive. In some cases it feels "jerky", similarly to times of heavy pageouts. However, the condition is not associated with low memory and doesn't recover after a period of time. Graphics operations such as scrolling or moving a window, or even just typing text as I am doing now (I'm currently experiencing the symptom) cause WindowServer processor usage to spike inordinately. I can't see what WindowServer is doing with its processor time since, because it is owned by the "windowserver" user, I can't sample it using Activity Monitor.
At first, since the NBC site uses Flash and Javascript heavily, I thought that it perhaps was a problem with a beta version of Flash. I had been using version 9.0.20.0 and reverted to 9.0.16.0, but the problem still occurs. It's possible that an even earlier version, such as 8.0 might do better. I didn't test Javascript because the NBC site doesn't work with it turned off and there's no way to revert to an "earlier version" of Javascript.
However, I then noticed that seemingly the same symptom occurred two other times under different circumstances - once at cbs.com (which uses Real video) and once, strangely enough, while downloading a RAR file. The server misrepresented the MIME type of the RAR as a .txt file and, since I had it downloading from a background tab, I didn't realize that it was loading 17 MB worth of text into the Safari window instead of downloading to the Desktop. I switched to that tab and tried to stop the download around 11 MB, whereupon Safari stopped responding and the whole system bogged down until the file (and an AVI file downloading properly) finished downloading. That's when I noticed the WindowServer slowdown I am now experiencing.
If anyone has any advice about this (or can kick Apple or Adobe or Real or somebody into doing something about this) I'd appreciate it. I'm going to try reapplying the 10.4.8 combo updater and see what happens. Also, below I've reproduced the graphics sections of two Xbench tests representing "before" and "after" scenarios. You can see that OpenGL remains mostly unaffected, but Quartz graphics really take a hit.
Aaron
---------------Before---------------
Quartz Graphics Test 71.11
-- Line 53.54 3.56 Klines/sec [50% alpha]
-- Rectangle 57.66 17.22 Krects/sec [50% alpha]
-- Circle 59.59 4.86 Kcircles/sec [50% alpha]
-- Bezier 74.86 1.89 Kbeziers/sec [50% alpha]
-- Text 240.66 15.05 Kchars/sec
OpenGL Graphics Test 78.53
-- Spinning Squares 78.53 99.62 frames/sec
User Interface Test 51.48
-- Elements 51.48 236.26 refresh/sec
---------------After---------------
Quartz Graphics Test 11.40
-- Line 13.47 896.68 lines/sec [50% alpha]
-- Rectangle 5.38 1.61 Krects/sec [50% alpha]
-- Circle 8.41 685.90 circles/sec [50% alpha]
-- Bezier 35.71 900.71 beziers/sec [50% alpha]
-- Text 31.72 1.98 Kchars/sec
OpenGL Graphics Test 75.95
-- Spinning Squares 75.95 96.34 frames/sec
User Interface Test 4.79
-- Elements 4.79 22.00 refresh/sec
Quicksilver 2001   Mac OS X (10.4.8)   GigaDesigns 1.8x2, 1.5 GB RAM, Radeon 8500

Answer 1

Well, well, well. Don't I feel stupid. Guess I fell into the common scenario where the person experiencing the problem assumes it's because of anything but himself. The problem had been very reproducible with NBC, and I still don't understand how anything Safari does could affect WindowServer like I was seeing, but the problem did not reoccur with a clean user account (after restarting - the "corrupt" WindowServer seemed to affect all users the same). So I went back to my normal user and used Onyx to clean out ALL caches (App, Font, System, Kernel) for all users and, for good measure, had it delete "Temporary and obsolete items". Restarted again and now the problem doesn't occur even in my normal account, at least for now. I never found these freeware maintenance apps to be much use, since they never actively repair problems and most of their functions are placebos anyway (running the OS's maintenance scripts, prebinding, etc.). I never ran into corrupt caches before (if that's what it was this time) and so I didn't find that useful either. There's always a first time.
Thanks for your help.
Aaron