Unexplained Jitter

I've been working on a project (6 song EP) and until recently it's gone great. My rig has started to get really bad, as I can't even play back my songs anymore. At first I thought it was the Antress Modern series of puins I had, but have since deleted them from every song and from the system entirely and I'm still having the same problem. It's bad, and I have a client waiting on me to mix this EP. My rig: Focusrite Saffire Pro 40 > Windows 7 PC. I have a feeling it might be a firewire driver issue, b/c when I"m in the mix control and it jitters the FireWire driver will go from "in use" to "connected". WTF? It's driving me crazy. I can't even work on this project anymore!

*BUMP* Has anyone experienced this problem before? It seems to come and go, but I just have this feeling that Antress plugins are the culprit...could be totally wrong! That's the only conclusion I can draw after researching this issue. HELP!

The plug-ins can't harm after you remove them, "save as" the project with a new name and restart REAPER with that project copy. Did it ever work? If so, it was something else you changed or inserted and it would be great if you could remember what it was. Otherwise you can try an empty project if you get the same problem for starters. If not, you can try to disassemble (plug-ins) an affected project piece by piece to find the problem.