Restart your computer and try again. If that fails, reinstall 2.0 and try again.
If that fails, do you have anti-virus software or other background utility software on your computer? Are you trying to install onto a network drive of some sort?
No data was lost—it was just updating the translators or styles, and the unzipping operation failed. That shouldn't happen normally, so it's likely some problem on your computer or a corrupted download. To make sure you have the latest translators and styles, you can just go to Reset Translators and Styles from the Advanced pane of the Zotero preferences.
Upgrade Storage
If that fails, do you have anti-virus software or other background utility software on your computer? Are you trying to install onto a network drive of some sort?