Using Radioactivity 7.x-2.5, the call to _radioactivity_checksum_validate in radioactivity-bootstrap.inc fails as the comparison compares a hash of data which has had its quotes escaped against a hash of data which has not. Adding a call to stripslashes before generating the the checksum in _radioactivity_checksum_generate fixes this. There may be a more elegant fix, however, this worked for now.