This thread talks in detail about Bitcoin's use of hashing of ECDSA public keys to generate bitcoin addresses.
Executive summary:
bitcoinaddress = RIPEMD-160(SHA-256(publickey))
So you'd need to break both RIPEMD-160 and SHA-256 hashing algorithms. And the RIPEMD break would have to be quite extreme-- more than just "add some random data to force a hash collision" (which is how MD5 is broken), because it is hashing a SHA-256 hash, so you're not able to add some random data to be hashed.