Hi Peter,
It's been a while since we spoke, hope you are well.
We have not had to change anything specific to support Premiere 5.5.1 as this release to my understanding was mainly for Premiere bug fixes and improvements targeted at OSX Lion, not any new features for 3rd parties to support. Are you running Lion? If not, is upgrading to Lion an option for you?
I had quick look at the Adobe forum also and it appears some other folks have had similar issues to what you have reported with Snow Leopard (not BMD or third party specific either) After they updated to Lion, their systems seemed much more stable and snappier. You can take a look here:
http://forums.adobe.com/message/3949167#3949167
I also checked with our support team worldwide and they have not had any reports with specific CS 5.5.1 issues to date.
In regards to responding to posts, we jump on to the cow when we can but we don't monitor this forum daily as it is intended to be a forum for users. The fastest way to find out about anything like this or to get help if you are having issues is to contact Blackmagic Design support either via email or give them a call in your local region.
For something like the issue you are reporting, they could grab some sample files from you, your system setup to try and replicate, then you can walk them through exactly how you make this fall over. If they can repro the problem with you they will then contact us with all of this information so we can look into it further and hopefully find a timely resolution. We speak to the support guys globally on a daily basis.
If you are running Lion and still having the same issues, then please contact our support guys so they can get all of your information, system setup, sample clips etc.. so they can can send a detailed report to us - then we can check it out straight away and hopefully see the same issues so we can try to fix it!
Regards,
Matt
Blackmagic Design