Check what graphics drivers you use now, because graphics can go into fallback mode, if something unexpected happens.
That means the current used graphics driver doesn't support some desktops 3D elemens, so you can't get into correct desktop look.
You can see graphics drivers in system settings -> system information, graphics tab - > what is driver?
Example a lot of people had issues when they updated Cinnamon 1.3, because by accident it also installed nvidia driver.
There is Clem's instruction how to fix that. Now the Cinnamon 1.3 is fixed, so that should not happen anymore.viewtopic.php?f=208&t=94842&start=20#p543183
Asus P7P55D, i5 750 2.6Ghz, 4GB DDR3, radeon 5770, 80GB Intel SSD, Dell 1600x1200, Dual boot, Linux Mint 14 Cinnamon, Windows 7