OP, was this $100 balance from purchases, or from Tell-A-Friend referrals? According to their T&Cs, the Tell-A-Friend referral payments do not count towards the $5 minimum required for payout. However, as long as you had at least $5 in purchase CashBack, you should be receiving a payout...
Sometimes it does take them some time to process. Last time, I received mine a day or two late.