FPS lagg in BGs

[davegeri]

Hey!
My problem is, that i have screen freeze and FPS lagg in Battlegrounds. I deleted my Cache/WTF, disabled all addons so now im playing without addons, configurated my videocard to the lowest and highest rates, but nothing helped. I've never had this problem on other servers, just here. I changed my Config.wtf setups what's good, because now i have 60 fps in 25 raids, but in BGs it crashed... Im playing with "No Install" WoW, so I cant Reinstall it.
Anyone have an idea?

[Dietrying]

I get random fps lag spike on BGs when i play with my 5 characters (i am multiboxer).
Lag spike drop my framerate from 100 fps to 2 fps, in random WOW window (i always open 5 windows with WOW)
I cant do anything with my character, that got lag spike.
If i press ALF+F4, i get 134 error message in window with lagspike...
Another 4 WOW windows (without lag spike) are close without any errors.

My config:
CPU: Intel Core 2 Quad Q9650 @ 4Ghz (4 cores)
RAM: 8 Gb DDR3 (1333 Mhz)
VIDEO: Ati hd5850 1Gb DDR3
HDD: WD Raptor (10k rpm.)
Windows 7 x64 (with all new updates)
2 Mbit Internet

I play with med. settings and 1680x1050 resolution.

My system are 100% stable in any games (and applications), except WOW.