I "fixed" a bunch of my tags using WinXP's built in properties.
I selected a bunch of mp3s in Explorer, right clicked, went to the Summary tab, clicked the advanced button (if necessary), click on any one of the tags, changed it and hit "apply". By having XP re-write all my tags, Wincab was able to see them all as they should be.
The obvious downside to this 1-click solution is that you're changing at least 1 tag in every mp3 to be the same thing. But you can also do this by album or artist, so you don't really end up changing the info at all. Select all your Barry Manilow mp3s, go through the above process, click on the "artist" tag and then click somewhere else. I don't think you even have to change anything to get the "apply" button to become active. Or, if you have to, just backspace over the "w" of Manilow and retype it. I didn't do it with every one of my mp3s, but it seemed to solve all the problem tags that I encountered.