Krell HTS 7.1 Problem

I am using a Krell HTS 7.1 processor in my HT system. Most of the time it works extremely well. However, occasionally I loose the center and rear surround sound. L+R and subwoofer seem OK. I can restore everything to normal simply by completely powering down the unit and powering back on. I am using an optical link between my Blu-Ray player and the Krell (current firmware, 3.4 I believe). Any idea what is causing this problem? I suspect I will have to send it back to Krell for repair.
I have some quirky issues every once and a while with my S-1000 processor. Sometimes when switching between DD5.1 and DD PLII + Surround, the Center channel becomes the rear left, the rear left becomes the center, the RR becomes the Sub, the L, R are fine..... VERY VERY Strange. Has happened 2-3 times, and I am fairly certain it is due to the video switching of the Comcast cable box (Motorola HD DVR). Like when the signal switches between DD and PLII channels. Anyway, a reboot fixes it. Hope this helps.

Mgattmch: I had a similar problem with my HTS 7.1. The left channel kept disappearing and I would have to power down and leave it unplugged for awhile before putting it back on line. Eventually that didn't help either and I had to send it into Krell. When it got to them the left channel worked fine - figures. They told me that sometimes the bumps and bangs of shipping can somehow put it back in order but, that not withstanding, they downloaded the latest software to it and shipped it back. It has worked flawlessly ever since. I am very careful about changing venues with it though i.e. switching from DVD to CD, etc.. .always best to turn down the volume and shut off one (say the CD) before firing up the DVD, etc. My work was done under warranty - no questions asked.
I also have my HTS 7.1 connected via optical and while watching satelite(bell pvr) the CC seems to cut in/out but not on any other selections(CD,DVD,etc)
Firmwear is 3.4
This is annoying,anyone have this problem solved??