I have released a new patch release 2.0.1 of the MD5 implementation for Common Lisp, which fixes a bug on 64-bit releases of LispWorks, that would lead to wrong digests being generated at all times. The new release is available from its PMSF page, and its GitHub home.

Note that MD5 has been cryptographically broken, and should therefore not be used in situations where a cryptographically secure hash function is needed (you might want to consider using my implementation of SHA-3 in those situations instead). However due to its wide historical use and its remaining suitability in non-cryptographically secure settings, this implementation is still of some interest.