Comment 2 for bug 1069081

If you have both system available, you can try to compare them and find which application take more memory, or which service is in 12.10 and not 12.04. For this, don't forget to enable all the process in lxtask (go to View => check all the checkboxes).
As far as I know, we didn't add new services that take that much RAM. So, it may be one specific process which need more memory in 12.10.