Can you try removing your website connection (if you have any drafts, discard them) and then re-connect to your website and try editing and publishing the web pages?
If this does not work, can you try clearing Preferences by deleting the Adobe Contribute 6 Preferences file from <UserName>/Library/Preferences/ folder. Also delete the folder Contribute CS5 from <UserName>/Library/Application Support/Adobe/ folder. Here '<UserName>' is the user's Home directory. By deleting these, your website connections will be removed. Launch Contribute and recreate your website connection, and try editing and publishing the web pages in your website.
Hope this helps.
I have the same problem. I have tried
1) deleting the .LCK (didnt help)
2) removing connection and remaking (didnt help)
3) reinstalling contribute (didnt help)
4) removing the cs5 app support files: e.g. rm -R ~<myusername>/Library/Application\ Support/Adobe/Contribute\ CS5/ (didnt help)
5) removing the app preferences e.g. rm ~<myusername>/Library/Preferences/com.adobe.Contribute.plist (didnt help)
6) called adobe support. awaiting callback, but they tried the same as above. (didnt help)