I recently installed Mavericks and FInal Cut Pro 7 seemed to run well.... until I tried to render some archival footage of various flavors that I had been using with zero problem with FCP7 and Mountain Lion. Then I began getting errors: "general error." Or the clip would render then appear white, or various styles of distortion. I tried creating a new timeline, new project, no change. I rebooted from a drive with Mountain Lion, opened the project, no change. I tried rendering small parts--some rendered okay, some didn't. I even took the project to another computer running Mountain Lion, same issue. I ran Digital Rebellion's software to look for corrupt files--there were none.
So then I opened a version of the FCP project from weeks ago, instead of projects saved under Mavericks, in Mountain Lion. I dragged the same seemingly problematic video files into a timeline, hit render, hurray! No problem, perfect playback. I therefore believe the issue was the way the FCP7 project was saved under the Mavericks OS. It's important to note that my standard files from my original shoots--with limited testing--seemed to be handled fine. It was only imported archival footage from various sources, of different flavors and speeds that seemed to be "corrupted" in a FCP7 saved under Mavericks, including some downloaded and imported only the past few days.
This might be a good caution for those whose projects use archival and downloaded video. I realize that some would just say turn it all to Prores. This would really suck and be extremely time consuming as I have thousands of clips collected over the years and often audtion dozens before choosing which ones to work with.
For now, I am going back to Mountain Lion, as it seem possible Apple may not resolve whatever this apparent conflict is between FCP7 projects and Mavericks. Hoepfully they will.