Don't know if anyone experienced this : I did an upgrade from 0.9.5 to an existing database, and tried the simple upgrade process - since I didn't need to change database info - but it failed and I had to do the install with the edit DB settings option. I am running MySQL 5.0.22 and PHP 5.1.6.
+1 with php 4.4.4 and mysql 4.0.25
Also : when putting the site offline/online (in Config > tab settings) : I get an error from Firefox 2.0 about a script I can stop or leave. After a while, if I stop the script, setting is saved. (Don't know if I'm clear... let me know ^^)