DB upgrade to 1.0 failed

[stefanx]

Hi!
I run Roundcube on a standard webserver, cPanel based and without shell access. When upgrading from 0.9.4 to 1.0, I access the /installer/ through web browser and the first page goes well. On the second page when pressing the button to update the DB, the server keeps running and ends with Internal Server Error after a while. The DB seems not to have changed, since it still works with version 0.9.4. Any ideas how to nail this problem down? Thanks.

[SKaero]

What is in the error log?

[stefanx]

No log is available in the "logs" subdirectory of RC. Also the logs of my webprovider don't contain any related information. :-(