by Anders Jakobsson.
Thanks for your answer. The account used did have highest possible accsess rights. As for the file system rights, the previous updates all the way since 2.0 has gone ok.
I do have a sandbox site and did the installation there first, and everything was ok there and that site is still running 2.4 nicely.
I probably will wait for a while for my themes and plugins to get to 2.4 and then try again.
Thanks fo your suggestions and ill post when i´ve tried again.
Anders