COH test client unresponsive to input

Since it seems this is a better, and more active location for what seems to be my issue than the I17 specific forum I initially posted it in, I'll drop the problem here. Sorry for double-posting.

Operating System (Vista, XP, OS X version): Windows XP Pro
User Client (Mac, PC, Linux): PC
Server: Test rooms (client-wide problem)
Zone: Any
Character name: Any

Graphics card: ATI X1600 Pro (AGP)
Drivers: Legacy 9.11 (since 10.2 was discouraged, this is the next one down for this generation of card)

Bug Description:
Trying to start up a (freshly downloaded) COH testserver client, I run into the problem that, after the extremely slow connection to check from the COH updater, the game loads up, but is extremely unresponsive - even at the login screen. I try to type my name, and password, and with some luck I get one character echoed every 5-15 seconds. It will be like that for a while, then it will briefly have normal frame rate for 5 seconds or so, then back to the total system lockup sluggishness. (even the mouse pointer).

The normal "live" client doesn't display this problem, just the testserver client!

Safe mode displays exactly the same problem.

I patiently poked around a bit more, and it seems to be strictly input related. The moment I click my mouse or press a key, the client chokes up (most of the times -- sporadically, it doesn't) for 5-20 seconds, after which it may or may not accept the input I had given it. If I don't give any further input, mouse pointer responsiveness and animations are smooth.

Any suggestions on how to fix this?

Other sysinfo:
CPU Athlon64 3700+ (single core)
2GB RAM
PS/2 Mouse (Logitech)
PS/2 Keyboard
USB graphic tablet (tried with it disconnected, made no difference)

At any point, did you get a pop up at the log in screen telling you your video card can handle Ultra Mode? If you did, and clicked the option for full on Ultra Mode, it can slow the bacon out of your card...

I was keeping my Test install updated, and trying to see if I was in the DB for the majority of the DB (until I got in near the end), and when they added that prompt, I chose the full Ultra Mode option. Then, I got the problem you're describing.

In order to fix it, I ended up dealing with the slowness of logging in, chose an empty slot, made a new Hero with no costume, went to the Tutorial, and turned off all UM settings. Cleared it right up. Then, I spent some time tweaking things to work for me.

Note that FSAA and Ambient Occlusion don't seem to play well together. And for me, I had to turn both off, or I'd lag like mad.

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Biggest Troll on the forums? I'll give you a hint:

I figured out the problem. Seems the new client doesn't like the multimedia keyboard software for my Compaq keyboard. Killing the driver for the extra buttons before starting the test client fixed it.

No problem. Glad you figured out what the problem was.

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Biggest Troll on the forums? I'll give you a hint:

I am experiencing this problem too. I am not sure what driver I can kill to fix it though...