Default [Q] Can't install zip in recovery


I use Mackay ROM 1.7 ICS and I switched to Gear kernel like a week ago.
All was ok..

Today I decided to go back to Mackay kernel. So I rebooted to recovery, pressed "install file from zip", "Install zip from SD card" and it says "Can't mount /sd card" or something like that..
Both with the internal and external.

What can I do?