It's all speculation at this point. We don't know all the details, and who's really pulling the strings. We do know that Venture Capital is involved, and when things are not moving as expected, I would think these guys have a voice.

As for MtGox, they've had lots of things to deal with lately, and as such, the transition may not have been in the front of their minds. I don't know. Coinlab has claimed that MtGox has tried to 'ban' some of the Coinlab customers, but I know no details about this.

Also we do not know under what conditions the initial agreement was made. There are many things that's unclear at this point.

 Probably. 

He will want it to go back up then though!

It's not about crashing Bitcoin, it's about being able to conduct business.  Coinlab apparently can't conduct business because Gox isn't meeting the terms of their agreement.  
 
Contract
http://www.scribd.com/doc/139181173/Contract-between-Mt-Gox-and-Coinlab

Complaint
http://www.scribd.com/doc/139281443/Coinlab-v-Mt-Gox

It's just business, Gox only entered this agreement to prevent CoinLab from becoming a competitor, then failed to provide the services on the timeline they contractually agreed to.  All US and Canadian Mt.Gox customers were supposed to become Coinlab customers on March 22 - Anybody remember that happening?

Because when you ship $500k into something and sign an agreement and the other party fails to fulfill their end of the bargain, you have to do something about it.

You have to understand that the conflict that underscores a law suit like this doesn't start the day the suit is filed. Undoubtedly for months Coinlab has been trying to get Gox to fulfill the reason Coinlab gave them a half mega. This involves months of phone calls and letters between Coinlab's upper management and Gox's upper management, as well as months of demand letters, most likely more than one, from Coinlab's solicitors to Gox's CEO and solicitors.

This is the real world equivalent of getting grimmed on a ~5000B transaction. After some time of not getting what you paid for and exhausting all reasonable methods, you call the guy who grimmed your 5000B out in public.

Whether or not there's merit to Coinlab's claim is something that will be metted out in the next several months. If there is, you'll see it settle at some point early on. But there's also cases where suits drag on for a long time even though one side admits liability, because the real dispute is the amount/substance of damages to be paid.

So really, it's not that he's trying to crash it. This is business in the real world, and unless Coinlab's case is super unmerited they're probably not wrong to do this. I doubt their case would lack in merit or solicitors of Susman Godfrey's level wouldn't even take the case, let alone spend the huge number of billable hours that go into the process before filing a claim in US Court.

Buy when the market tanks and then sell at the high point. It's called scumbag surfing