The only thing worse than finding a bug in your client is finding half a bug.
Hi everyone. 
Some residents have been contacting us in support with problems that seem to have arisen since upgrading to 1.20.15 (formerly the Release Candidate)
While we strive to eliminate bugs in an RC client before it becomes an official viewer, there is always the possibility of problems we did not previously discover. We cannot test on every conceivable hardware configuration before release, so we rely on your feedback to find these when or if they do occur.
If you have a problem that seems to be a possible bug related to the 1.20 upgrade on your system (or if you want to revert to 1.19.1.4 for any reason really), the first thing you will want to do is remove SL from your system and then reinstall the previous version.
How do I fully uninstall and reinstall Second Life?
You can find the 1.19.1.4 installer downloads here:
Windows
Mac
Linux
Once you have verified that the problem does not exist in the 1.19.1.4 client, please let the developers know this through the Issue Tracker. If it is not limited to the 1.20.15 version please create a ticket in the support portal and we will do our best to help resolve it.
The 1.20.15 update is an optional update. You can continue to use the 1.19.1.4 and 1.19.0.5 viewers as they are still supported.
Thank you