I made an offer on a condo last week, that's been accepted, but i'm not sure that i want to move forward. What are my liabilities if i decide not to sign the contract?

Check with your attorney, but you probably don't have significant legal exposure. One unfortunate consequence is that the listing agent may spread the word in the broker community that you're a flake, and your offers should not be taken seriously. That might be a concern if your search is focused on a narrow market segment dominated by a few brokers.

If you didn't sign the contract you should be fine, but tell them ASAP.