After the closed beta access to everyone hiccup on Sunday, some people did an uninstall and then a new install. The install happens just fine with no errors, however most of the data is gone due to the previous uninstall action.
You see, it appears that the installer moves files from the download directory to the install directory instead of copying them. So, when you uninstall, they go bye bye.
If you don't want your download files messed up when you install (i.e., you want to keep a copy in case you need to re-install later), make sure you copy the download directory before doing the install.
Hope this helps. I expect many many many players to have this issue come Tuesday morning, and they are likely to be a bit ticked.
Afterall, who opened up beta to everyone yesterday anyway?