After this happened, I couldn't go forward with the upgrade. I had the last 1.1 RC version, uploaded all the new files and called the upgrade script. Everything seemed fine until I got to this stage.
"Error retrieving information on step: Adding new custom field columns (Item: 14)"
(http://www.elkarte.net/community/index.php?action=dlattach;sa=tmpattach;attach=post_tmp_724_52be15ec085c5bc53e790bee771b25e4;topic=0)
You need to run the upgrade only if you are coming from 1.0, not if you are using any 1.1 beta or rc.
In this case, just overwite the files and delete the install directory (or do not upload it at all).
oh crap
It shouldn't break anything anyway.
Though the bug is still valid, because it makes sense to detect the version and decide if the upgrade should be run or not.
Fixed locally