I'm brand new to mods and have gotten quite a few to work with the help of FOMM. I just tried installing MMM but for reasons unknown to me, MMM is crashing FOMM. I am no longer able to get into the Package Manager at all and have no idea how to get rid of MMM in order to get there. Help would be greatly appreciated. Thanks.

MMM can be resource intensive, I'm trying it again with my mod load on a quad core and notice slowdowns, and works best if I reboot fresh and don't have the GECK open, a browser with 42 tabs etc (wyre flash was svcking .5 gig memory, HOLY COW) but I've removed other mods such as S Storms and EVE and don't have FWE, and so far it is not too bad.

To remove mods other than ussing FOMM you could try Wyre Flash (bash) whatever, or just go directly to the fallout data folder and move anything Marts Mutant Mod xxxx to another folder or even the trash

I f you just want to remove the FOMOD from the package manager, they are stored in the FO3 main directory in \mods. Delete/move MMM's FOMOD and FOMM will no longer see it.

Strange problem...

It is indeed a strange problem. I was however able to get it to work. Somehow, after trying to open if for nearly the 11th time, the Package Manager opened and I was able to activate MMM. Not sure what happened this time but it worked.