AFAIK "sick" only means that it has spent too much time without bfgminer detecting a share. It can be normal, if the pool is rejecting low difficulty shares (as the miner takes a long time to produce high difficulty shares). It will stop showing "sick" when the miner throws a share over the pool difficulty.

Some pools adjust difficulty and lower it down to your stick miner; others don't. Try just leaving the miner running for a while and the sick might go away when a share is submitted, then declared sick again if much time passes without a share.