Found a fix for this on steam support:
http://support.steampowered.com/kb_arti ... -ERFB-3416
Please follow the troubleshooting recommendations below to resolve the issue:
1. Load the game
2. Go to the Find Servers option
3. Switch to the Favorites tab
4. Go to the Change filters button
5. Select "Secure" from the Anti-Cheat drop-down menu
6. Exit and then reload the game
7. Go to the Find Servers option
8. Switch to the Favorites tab
9. Click the "Refresh" button
If you could see servers through STEAM -> servers before you should be able to see them in the game as before.
If this method does not work at once, delete file serverbrowser.vdf and repeat the recommended troubleshooting steps outlined above once more (by default, this file may be found at C:\Program Files\Valve\Steam\config\ - otherwise, find the Steam directory you specified when installing Steam).
Note: Saving favorite servers through the Steam server browser is currently a more reliable method for storing the server information.