To reach Avid / Pinnacle Support, the best you can do is find some threads where its representatives have posted recently and send them private messenges. But they can only forward your observations to QC or something, and may never hear back.
Employee mpingel is Pinnacle's Dr. Von Braun, so far as AVCHD / h.264 goes.
This is the sort of thing that a a patch might fix, but require consolidation with other things that such a patch must address. If you get your observation in the queue, perhaps it will qualify.
Meanwhile, you might inquire at the Vegas or PD8 forums whether any users own your model and how they edit the video. PE7 is another product, but tends to be slow on introducing support for new formats.
Free trial versions of such products are often available, but sometimes only for standard definition.
I'll concur with pratically any complaint you might have about the weak or ambiguous disclosure the products provide for their format support. The irony is that some manufacturers implemented the other variants of h.264, precisely because the AVCHD was too dense for some PCs to edit, but are in fact harder to edit because the NLEs don't import them properly. The disjuncture in sound and motion is a problem. Sometimes the conflicts don't become apparent until the timeline exceeds a certain length or until the project includes various edit effects.
Good luck.