Upgrade to 2.3 fails!?!

Gallery version: 2.2.6
PHP version : 4.4.9 or 5.2.6 (I tryed both)
Webserver: Sun OS
Database MySql: 5.0.51
Operating system: Win XP
Browser Firefox: 3.0.4

While trying to Upgrade my gallery2 from 2.2.6 to 2.3 it always fails in step core modules!
When he is "Creating Package Map", he always stops on diferent packages and "freezes" the process!
Firefox says "ready" in the bottom Line!?! No more ativity...
No matter how often I re-start the Upgrade-"core module"-process, it always stops on a different package position, but it defintly stops and never succeded!

Here are my questions:

1. What can I do to avoid this error?
2. Is there somwhere an error log?
3. Can I cancel this Upgrade Process and go back to my 2.2.6 version?

Thanks for help...