It is set to be fixed in 1497: http://www.mediamonkey.com/forum/viewtopic.php?p=340672#p340672

Using metaflac I can see that the tag doesn't get updated with a blank.

Put another year in, it updates.
Blank it, it changes the timestamp on the file but date is still the previous entry.

I was under impression that clearing tags would work in MediaMonkey 4, however clearing date in some FLAC files failed for me too: http://www.ventismedia.com/mantis/view.php?id=9402

Turning of Infer File Properties cleared up the track listing issue and exposed many more tags that weren't set.
That was a good start.

I still can't blank out the year though and not sure where that is being picked up.
In particular those that show full date (eg. 02/10/2003 instead of just 2003).

Tools > Option > Library and disable Infer File Properties as this is the setting that allows MediaMonkey to guess tags on scanning. You can do this tagging from filename manually using Tools > Auto-Tag from Filename with full control on how and what it tags.

Filename                                             Track
38 Special - Caught Up In You.flac                    38
999 - Homicide.flac                                   999
Beastie Boys - 01 - Girls.flac                        1
Beastie Boys - 02 - Fight For Your Right.flac         2

Filename                                             Track
37 Special - Caught Up In You.flac                    37
998 - Homicide.flac                                   998
Beastie Boys - 02 - Girls.flac                        2
Beastie Boys - 03 - Fight For Your Right.flac         3

One thing I found is if the filename contains a number, it automatically becomes the track number in MM and can not be blanked.

[code]
Filename Track
38 Special - Caught Up In You.flac 38
999 - Homicide.flac 999
Beastie Boys - 01 - Girls.flac 1
Beastie Boys - 02 - Fight For Your Right.flac 2[/code]

If I change the number in the filename then the track # again automatically changes in MM.

[code]
Filename Track
37 Special - Caught Up In You.flac 37
998 - Homicide.flac 998
Beastie Boys - 02 - Girls.flac 2
Beastie Boys - 03 - Fight For Your Right.flac 3[/code]

So it looks like MM is trying to "help" by automatically filling in a track number.
Is there a way to turn this off?

Blanking the year or track # on other files is still an issue.

This is really driving me nuts.

I have a rather large compilation I'm trying to cleanup the tags on.
When I blank out a particular tag (eg. Year or Track) it shows correctly and the timestamp on the file is modified.

However if I exit MM or navigate to another folder and back again, the original contents of that field is back.
If I put something in the field (0 for track for instance), it updates correctly and navigating away and back it is still there.
If I blank out the field again, the original contents of that field is back.

"Update tags when editing properties" is selected but I have also tried Synchronize Tags before navigating away with no luck in resolving the issue.

Are my flac tags corrupted??

I don't see this behavior with mp3 files in the same folder.