It's occured for me first under win 7 & now under win 8, on 2 different PC's using both G-Blade & Orbs. I've looked at power supplies, Com Port settings, cabling..you name it. IMO its some sort of 'initilization issue' as either the miner/s will kick off and start accepting shares or they wont (until next time bfgminer is restarted & the device/s are reinitialized), though I have seen cases where a miner will accept a couple of shares then nothing.
If you are using MultiMiner and have it set to restart "suspect" miners it should pick up on miners that have a low effective hashrate.
Also note that, depending on the pool difficulty and luck, it may take a bit for things to play out.
Yea it is set to restart and I've let the miners run for quite some time with no shares. I'm wondering if this is just erroneous reporting in MM? I'll try running the miners from bfgminer directly and see if I still get zero shares accepted. If I dont, I'm going to somehow have to try and do a compare between shares reported in MM versus actual shares accepted on a pool.