[Slim Shady]

Focusrite Liquidmix isn't listed on any Digi PT compatibility docs that I can find. From what I'm reading online, it's an external DSP processor that uses RTAS wrapped VST plug-ins to operate? That's like trying to cook your dinner after wrapping it in an old sock and then holding the pan 6 feet from the stove. You're just adding layers and layers of incompatibility (not to mention latency), which is not really a wise move. The -6097's are probably a direct result of having the Liquidmix connected, it's probably sucking too much from the firewire bus causing PT to lose it's connection with your interface while the Liquidmix takes all the juice.

If you can get something like that to work without any errors, I'd be pretty impressed. It's definitely not supported, at least I can't find anything on Digi's site that says they support it, or even mention it for that matter. They didn't support the fxpansion PCI cards (very similar concept, and also resulted in tons of errors), and since Digi makes their own version of "offloading DSP to other devices" called TDM/HD, they're not likely to support any 3rd parties trying to do add that feature to PTLE.

I couldn't find much info on ARC either, but it also isn't listed on the plug-in compatibility grid. It might be that it's too new, because I believe most of IK's other plugs are finally 10.5-ready (but require updates), but you might want to double check with them to make sure the latest version is compatible with PT on 10.5 - there are still lots of plug-ins out there that aren't.

What if you remove the Liquidmix and the ARC? Any errors? (BTW, remove means to move the plug-in out of PT's plug-in folder entirely before booting PT). Basically you're going to need to do some troubleshooting on your own to figure out the culprit. If removing those guys doesn't solve it, remove any other 3rd party plugs, then add them back one by one until you find the nasty one(s).