sporadic distortion in low end?

I have pretty cheap-o vinyl setup with a Music Hall MMF-2 and a Benz Micro MC20E2, and admittedly, don't know too much about this sort of stuff, but have been having a problem for months that I am just now getting around to dealing with.

On a few records of mine I am having problems with low-end distortion. The particular recordings I am having problems with have a really open kick drum, that when coupled with certain notes in the bass line produce a distortion so severe, it can skip the record. I can counteract this increasing the tracking force, but even when I get beyond what seems like a comfortable weight, it still distors, but doesn't skip. I don't have a stylus force gauge and set up the cartridge myself (although I had help and feel pretty confident that it is aligned properly).

Problem is that it is really sporadic. I have only noticed this on two different records (both by the same artist and pressed at the same plant), which almost leads me to believe that it could be a pressing flaw, but I feel like other people I know with the same record would have this problem (which they don't), and I don't remember having this problem when I had a basic technics/Audio Tecnica setup for records. And, most everything else I listen to sounds really good.

Any ideas? Maybe my cart is messed up? maybe I just need to get someone to professionally set up the cartridge? maybe the size of the cart screws up the VTA too much?

IF it is a record flaw (it seems more a vibration issue /setup from your post) repeat the same passage with your former lightier tracking force but do it with the volume all the way down. If skip persists is a disc or arm setup problem. If problem is absent need to take a look at where and how your TT is setup.
What attracts my attention is on loud kick drum passages. Describe your TT setup specially rack and floor in your room (wood by any chance?) have you tried moving the TT to another place where maybe bass reinforcing in your room could not be a factor?
Dear Pablo. It looks to me like a classic problem between your tonearm/cartridge resonance frecuency. Your cartridge don't mates with your tonearm and the only solution is to change that cartridge or to change that tonearm.

In theory, the resonance frecuency between the cartridge and the tonearm has to be between 8 Hz to 12Hz, where the efective mass of the tonearm and the vertical compliance and weight of the cartridge are the parameters that define that resonance frecuency.

Regards and enjoy the music.
Although i haven't done this just yet (am at work) i know the first time i heard the distortion i listened on headphones and had the same problem. So perhaps it is a arm/cartiridge issue as Rauliruegas pointed out?

Do you have any more info or web reference to calculating this so I know what kind of cartridge is compatible with my arm (the arm not being replaceable since I have a low-end Music Hall)?

Pablo: f= 1/2Pi x the square root of 1/mc. Where m is the effective mass of the tonearm + the cartridge weight, c is the compliance of the cartridge and 2Pi is = to 6.2832.
That's all you need.

Regards and enjoy the music.

Your experience with the headphones points definitely to Raul's suggestion (right on the money!). Keep us updated on your progress.

thanks! i know cart. compliance and weigt, but effective mass of the tonearm? is that just the tonearm's weight? i should just ask music hall for that?
Pablo: You have to ask to Music Hall.

Regards and enjoy the music.
Well, Music hall never replied to my queries about the tonearm mass, but i picked up an old grado G2+ for cheap and just put that on this weekend. bass issues all cleared up. This cart is a lot different than the benz, and while i like the sound, i don't like it as much. but it fixed the probelm with the bass. We'll give this a go for awhile and see if any other issues come up.