Technically speaking, yes, there are attacks faster than brute force.
BitLocker uses the AES algorithm for encrypting the data on the disks, and there is a known attack against AES that provides about a three-fold speedup over brute force for AES-256, and a four-fold speedup for AES-128. Still completely impractical, so if you need to decrypt something without having access to the password, your best bet is still something like a side-channel attack or a $5 wrench$5 wrench.