It could be that the particular card you're trying to use is being blocked for some reason (maybe the credit card company recognizes the attempted transaction as that of an online sportsbook and is therefore blocking the charge). Just today I did a credit card deposit over the phone on my Bookmaker account, and it was credited with no problems.
I hear you though...it does seem as if most sportsbooks have their fair share of issues. I remember a couple of years ago Sportsbook.com had HUGE payout issues...it took FOREVER to receive your payout via check.