In Pro Tools v5.0.1, recording takes to a track called "Guitar" would result in files called Guitar-01, Guitar-02, and so on. In PT v5.1.1, those same takes are now named Guitar_01, Guitar _02 (using an underscore as the connecting character instead of a hyphen).The Reason for the change is as follows:If you recorded a file "fred-01", it would show up in the bin as "fred-01-00". The first edit of it would be "fred-01-01".Now, if you removed that file and reimported it, or track transferred the track into another session, it would import as "fred-01", NOT "fred-01-00". So what would happen is that the first edit would be "fred-02" - If you were trying to keep track of take numbers, this was a TOTAL nightmare. In some cases users would have to employ software such as Gallery's Session Browser to change all the file/region names to underscored ones - because if the file was named "fred_01", upon reimport, it would still show up as "fred_01", but the first edit would be "fred_01-01"A very simple solution was to have file names have an underscore.