Just a quick question.

I have a Denon receiver (AVR-2106) that I am using to run my Jamo X870 speakers that are 4ohm. Thing is the lowest recommended impedance for my receiver is 8ohm so what kind of problems can i expect?

Reason I am asking is because for the past year I have been using it like this with no problem but now suddenly every hour or so my center speaker shuts off. I replace the center speaker with another one I had and it still did the same thing. When I swapped out my jamo speakers with some infiniti ones just to try it out, everything is working fine again.

So is it most likely I am now suddenly having a problem because of my low impedance speakers?

thanks

Yes the 4 ohm is a problem with overheating. Your owner's manual page 5 describes the condition. See:
http://www.usa.denon.com/AVR2106_DFU_ownersmanual.pdf

thanks, all this time i was looking at the back of the manual not the front!

anyways seems i am really overdoing it since i am running the 4ohm speakers as biamp so 4x4ohm which is too much for my amp. i guess its gets new speakers or a new amp now..

If you like the speakers and don't want to change/upgrade, get a new amp. If you don't like the speakers or want to change/upgrade, get new speakers.