You can try calling them or writing them and explaining that you sell digital goods, but this is about a 50/50 chance. They might call several of your customers to verify. If they won't lift the limit, go back and see if there's anyone you can refund that will give your money back through other means. I highly recommend anyone selling digital products with pp setting up a relative-to-usual-balance sized payment to a friend or family member every couple of months, cash it out and give it back to them (you can even just send it right back thru pp), that way if you get limited with money in there you can issue them a refund for that particular transaction and get some of your money back. If it's at all possible.
Don't totally panic if you end up getting screwed by paypal, it happens to the best of us. Just research payment processors for digital goods and you'll find another solution, albeit you'll have to wait longer to get your money to your hand.
With all this bullshit with online processors, Payko is looking better and better to me. It's an online money order service, straight to your door, no fuckin chargebacks or hassle.
But yeah I hope this helps. I have been through this myself as well as a close friend of mine, rather recently.
Edit: Also, MK is right, don't be afraid to get on the phone with them. As long as you're shooting straight, they should work out something with you.