Through various error reports and some direct contact, I was made aware that, at least for a time, Kaspersky antivirus products were incorrectly flagging a component of RD Tabs as malware through their heuristics engine. Heuristics engines are notorious for flagging false positives since it bases what it judges as malware simply on the profile of the application and not that it has ever been verified to be malicious.
The file in question is "Launch Remote Desktop Services Manager.exe" which is a very small (about 30 lines of code) app whose only purpose is to search for the Remote Desktop Services Manager MMC and launch it if available. RD Tabs will crash without it because there is some detection logic exported so RD Tabs knows whether to add the Remote Desktop Services Manager to the Tools menu.
It appears Kaspersky may have fixed this detection flaw already (I'm not sure, I don't use Kaspersky) as I am no longer seeing error reports coming in and the online scanner showed the file is safe.
If Kaspersky deleted or quarantined that file, you will need to restore it to use RD Tabs, or reinstall RD Tabs. Your settings will not be lost if you have to reinstall, so I suggest doing that just to make sure all the components are unaltered.
For RD Tabs 3.1, I'm going to eliminate the hard dependency on the component to the main RD Tabs application so RD Tabs will not crash if this file ever gets quarantined again.