I am having similar issues. I had an MU install that did not get the previous update, so I did this 1.3 update and now I have the funny symbols in several blogs too. (Â )
I had uploaded all files and did not overwrite the wp-config. Did the upgrade button in admin and then had the symbols. After reading this thread I renamed the original config file to -old and then used the new config file that unpacked with 1.3. I changed the /base issue and it seemed to work, symbols still there.
So I used my backup database and redid the upgrade script with the newer config file in place, and I still get the symbols. I tried going back to the old wp-config file and they still show up.
Any way to search and replace for these symbols across all blogs?
Is there anything about this issue in the readme (which I admittedly skipped since I backed up).
Should I have not kept the old config or sued the new one?