You could try to format your storage card and reinstall ML (read the installation manual for the process).
When you're running the latest 2.3 official release you might want to give one of the nightly builds a try (usually there's an every day release).
ML faced alot of changes since 2.3 release, for me it's working pretty well on my 550D.
When you encounter a bug please report it.
The nightly builds are easy to install and you can perform a rollback to 2.3 with no problems.
Go to Downloads and scroll down for the Nightly Builds button and download the latest.
Before you replace anything, make a backup of your storage card.
To make the Nightly work, replace the Autoexec.bin and the whole ML folder except for "doc" because the direct help wouldn't work anymore.
Cropmks, data and scripts need to be replaced.