I had this problem and today I found out most of my problems were happening because I loaded the OS 1.22 incorrectly. I would suggest backing up everything to PC and then loading the operating system again. When you do load the operating system:
1. Make sure it is on a newly formatted CF card.
2. The "MPC2500.bin" is the only file on the CF card.
3. Turn off the MPC, w/ the CF card containing the OS 1.22 in the CF slot.
4. Turn on the MPC and immediately hold down the Window button.
The OS should load and then restart the MPC.
Once this is done don't forget to reformat your hard drive.
When I did this everything seem to be working a little more smoothly. I am surprised the OS installed when I installed it incorrectly but we are talking about Akai!
Let me know if that helps
Holla
~Yung R.E.M