rampantone

Uninstall the razer software and try that, hook up a different mouse without the razer software. Do some research on them and game stuttering, could be on of those little stupidly simple things you were talking about.

Boatman are you using a Gigabyte motherboard by any chance? Or a Razer mouse? Have you made sure to configure your Power Options? How long have you owned this PC and does this issue only happen with Arma 2, how many other games do you play regularly? Noticed your hard drive is close to being full, you may want to try CCLeaner http://www.piriform.com/ccleaner if you don't already use it and take some time to remove any unwanted or unused programs to free up space on the HD, also give this program a shot http://diskmax.en.softonic.com/. You may want to research in to some newer BIOS for your motherboard, check out the boards site and read what people say about the different revisions before flashing. This is a last resort though, and i'm only mentioning it because I had to deal with this before with a Gigabyte board (switched from using ASUS for almost 10 years) who sent out a batch of faulty boards (knowingly) and flashing alleviated the problem but ended up RMA the board and sticking with ASUS.

Do you use wireless internet at all Boatman? Some other things you might try if not already is disabling your sound and the HD Audio, reducing the audio samples from 32 to 16 in the Audio Settings in game and run a DPC latency test and compare with others motherboards of the same model or type. http://www.thesycon.de/deu/latency_check.shtml

I had these with my 6850. The easiest way I found to get rid of it was turning off ATOC in the ARMA2OA config, ATOC=0. Disable PP for troubleshooting when you do this. If that fixes it then you can keep bumping up the ATOC by 1 and see what level works best, from what I've read this is an ATI issue. See: http://community.bistudio.com/wiki/arma2.cfg

Could be FADE?