We have a 5 system environment including 2 NLB servers, 1 authoring server, 1 SQL server, and 1 Forward Search Server. We currently only have CMS 6R2, and Composer 4R2 installed on our AUTHOR server and we are experiencing lockup issues where process w3wp.exe uses 99% of the CPU and our users can no longer author content. We originally thought it was related to CMO being installed but we have a new AUTHOR server that we have not installed CMO on.
Any suggestions would be great.
Hard to tell, I would take a dump of the running process when it is at 99% (you can use DebugDiag to do this automatically), then you need to analyze this process dump. After that you can use the <a href="http://www.microsoft.com/en-us/download/details.aspx?id=8279">debugging tools for Windows</a> to analyze the dump file to find out what's causing the high CPU usage.
For a nice screencast on this I recommend: Debugging Chronicles on Pluralsight.
Hope this helps