Husky, im not sure that rig can really handle the high res pack. Especially not with AntiAliasing turned on.
Also, with only 1 Gig RAM and 512/1024 textures, do NOT preload skins - they need 2.5 GB RAM. You can preload textures into system ram though. Make sure you also have both "optimize" functions checked.
As for sound: With the graphics on the limit of the ressources, you might just run out of them for sound. Do you have onboard sound chip or sound card? Are you using custom sounds (they need a lot more ressources as the default ones).
Another thing you can do is check your processes/system. The more you got running in the background, the less Aces High can take from your system. Maybe you can get out a little more, even though i doubt that helps much if you have the problems you describe.
If you cannot get it fixed, go back to 512 textures - that probably cleans it up.
Hope this helps you.