After upgrading from 1.5.2 to 2.0, my site just vanished.
1. Followed upgrade instructions from site.
2. Performed all mentioned copies and renamings.
3. Went to my "mysite.com/admin" page and I clicked on "Upgrade Database" which led to me a "successful upgrade" page.
4. Then I clicked on "Plugins" in my admin panel in order to re-activate my plugins.
5. Clicked "Activate" on the first one (CoinS in particular) and then it returned a blank page.
Now all my pages (mysite.com, mysite.com/admin), etc. are blank.
What went wrong??
Sounds like something is wrong in that plugin.
First step will be to turn on error messages as described here, so that Omeka will give us a little more information.
I had a similar issue. We had old plugins installed that were causing issues. Do you have any old plugins installed? Try running with just the default plugins, see if it is stable, then download any 2.0 capable plugins that you need. We had several older plugins we were trying to use and if you don't have error reporting on, it can cause the page to display as blank.
Did a clean re-install by migrating to the new setup only my old db.ini and nothing else. No themes, no plugins, as described in step #5 of Upgrading Documentation and everything now works fine.
The problem was not the plugin (CoinS) which was a "bundled" one with the 2.0 version but my old theme.
Now, I use the (updated for 2.0 version, I guess) "Thanks Roy" and I will start building on this one, from scratch.
Version 2.0 feels good and fast and smooth and beautiful BUT most probably I will only upgrade again only in really major versions/changes.