Did you try removing Outlook as a Data Source?
I have exactly the same problem and found the exact problem with installing/uninstalling that you found but have been too busy lately to look at X1 and the Data Source myself. I was hoping to be able to continue to use X1 for searching files. I expect a X1 Plugin injected into Outlook is the culprit. And fixes were being made to Outlook integration (for Outlook 2013) issues right up to the last beta releases. I would like to hear from X1 Support on this issue.
I have exactly the same problem and found the exact problem with installing/uninstalling that you found but have been too busy lately to look at X1 and the Data Source myself. I was hoping to be able to continue to use X1 for searching files. I expect a X1 Plugin injected into Outlook is the culprit. And fixes were being made to Outlook integration (for Outlook 2013) issues right up to the last beta releases. I would like to hear from X1 Support on this issue.