I have retried to upgrade, following exactly the stepts in the guidelines. The same result! I have downgraded once again. I got to writing the following line into my browser's address field:
It produced a white page. Then I typed in:
and got another white page while the address line changed to:
(Just one line)
What does that mean? Please, give me at least a hint where I can look for a solution. I never had any problems with upgrading so far, and I did not deviate from the instructions, so there must be something wrong here.