See http://developer.atlassian.com/jira/browse/CLMVN-26
merging database 1 of 3
ERROR: Error writing new clover db '/Users/new/Support/clover/multiproject/target/clover/cloverMerge.db': java.io.IOException: Not in GZIP format
An error message which explained that this was due to a change in the DB format would be nicer.