version 2.0 will convert your wallet file to a new format, which cannot be read by 1.9.8. anymore.
This is why you should make a backup of the wallet file, and check the integrity of your seed backup before updating, or more important when using BETA versions of any wallet software.
I have the backup of my seed written down offline and I believe that's enough. I never said I had lost access to my wallet, so I know what I was doing there by using the BETA version. I had also exported backups of my labels. And also as Thomas said that Electrum 2.0 converts the wallet into a new format and thus 1.9.8 wont read it. The converted wallet works well and good and I can access my wallet fine on 2.0, it's just that I had the doubt why it wouldn't run on 1.9.8 before, but now that's cleared.