1) Did you just remove Rhino 5.0 Beta?
Please download and install Microsoft Visual C++ 2005 Service Pack 1 Redistributable Package MFC Security Update. After installation, Rhino 4.0 should be able to communicate with the license manager properly.
2) Are you running Rhino 5 and did you just uninstall Rhino 4?
To reinstall the McNeelLM without reinstalling Rhino 4, download, unzip and run rhinolm_20110309_x86.exe which is in this rhinolm_20110309.zip file.
3) Running Windows Vista or Windows 7?
Make sure you're running Rhino 4.0 SR9:
4) Reinstall Rhino 4
Unfortunately, something is wrong with your Rhino 4 installation. Follow these steps to repair your installation:
4) Still not working?
If none of these work, see the Advanced Troubleshooting for License Manager Errors page.
Updated: July 28, 2012 by Brian Gillespie, McNeel Seattle