hashcows zero balance rounds

i've been mining on hashcows for the last few weeks now, and it is a great service and top operators. I love this site. They have been upgrading, I guess to deal with the load increase, and most things seem fixed now so that's great.

My BTC balances go up and down, but that is the nature of this and I'm fine with that. However I'm still showing zero balances on mature and immature rounds, this confuses me because the problem rounds are random (different in duration, so it isn't a reconnect delay on short rounds as pointed out on recent posts) and I'm converting all my coins to BTC. It isn't also the miner, it is a 5MHash machine, running cgminer 3.6.1 and ran very stable on other pools before this one. It also ran stably on this pool before the problems, reporting a non zero balance on all rounds.

The zero balance rounds are 5214-5217,5219,5222,5232,5234,5237,5241,5242 so far.

Cos I'm a newbie, I can't post directly on the hashcows thread, so I'm putting it here in the hope it gets picked up.

thanks

cuesta