What music is Warners concerned about rights issues with?

I hear on imdb time and again people repeating the same old reason as to why Warners won't release this excellent series complete on dvd - "music copyright issues means it's too expensive". To be honest I've always found this BS reason mildly ridiculous because there's plenty of other series with more seasons and more music to license and they manage to get onto dvd in their entirety. So WHY not Third Watch?

So can anyone speculate what well known songs in whatever seasons MIGHT be stopping the useless Warners from releasing this? It'd be interesting hearing what songs we could come up with any how many. I really bet it wouldn't be a lot.

The only one that springs to mind for me (mainly because like most of us I've not seen all the seasons since they aired) as being potentially tricky is the fact TW uses a well known song ('Keep Hope Alive' by The Crystal Method) as theme music which they'd certainly have to license for all the eps. Most series seem to rarely use an actual song for a theme tune preferring just some composed theme tune music by the series composer (The Sopranos, Justified and Damages being notable exceptions). I presume that's just a saving money issue?

So could the real culprit all along have been just The Crystal Method song? People's thoughts would be welcome because I'd really like to get to the bottom of this mystery once and for all. This excellent series DESERVES a dvd release ffs!