workspace switching via ctrl + alt + arrow not working after upgrade to 13.04, how to fix this?

I had this same issue. I enabled workspace from Appearance → Behavior, and also tried using Ubuntu Tweak, but no go on the keyboard shortcuts, even though all the defaults were there.

I then opened CCSM to make sure that the Desktop Wall was enabled. In my case it wasn't, and as soon as I enabled it, my keyboard shortcuts started working again.

This may help.

On my system, the same thing was happening. I found, by checking the Keyboard>Shortcuts>Navigation that it's not Ctrl + Alt + Arrow, you haveto press Ctrl + Alt + shift+arrow perhaps the C+S+A is being used bu another programme so conflicts.

On Ubuntu 13.04 workspace are disabled by default. To enable it open 'Appearance' from system settings > click to the 'Behavior' tab > check 'Enable workspace'. And also check the keyboard shortcuts in system setting>keyboard.