The Key to this problem is the modx_workspace table in the database.
After multiple reinstallations and cache clearing I was continuing to have the same problem as you. Keep in mind this was from 2.0.8 to 2.1RC
AND I was moving my modx install from a subdirectory to my core directory. I could tell this was the problem because the package manager said it couldn't install my package under url/newsite/....
I was no longer under my newsite folder for my modx install.
It seems the re installation doesn't change the modx_workspace table. At least in 2.1RC. So i just manually went in with phpmyadmin, fixed the workspace working URL and bam. fixed.
I can confirm this too ... the URL was pointing to the location of the old site and the DB table entry had not been updated. Which is probably my fault since this piece of information is in the MODx "Moving Your Site" Documentation.
