I've had this issue before. If I remember correctly, there are a few things that can potentially fix it.
1. Right-click the launcher icon and click "Run as administrator." Attempt login.
and/or
2. Open Task Manager (control+alt+delete), expand the list, and then remove everything entitled Bitraider. Then try a fresh login.
and/or
3. Right-click launcher icon, then click Open File Location, then delete the Bitraider file. Yes, delete it. This will force the launcher to run a quick repair, potentially downloading replacements for corrupted files.
If none of this works, try logging in at a different time of day. I found that, on bad days, there was a specific time (around 6PM-midnight) when this error message occurred unavoidably. The error ceased to occur after midnight.
I hope this helps.