I feel your pain: last year my car was squeaking. I was told "just polish and anti-seize the bushings..." no prob I though: I assembled my car shouldn't be too bad... One winter later :banghead: completely disassembling my car... it doesn't squeak any more :driving:
If the rivnuts are spinning, can you tighten them? I've done this with a long bolt, washer and nut: thread the nut onto the bolt, then secure the bolt threads into the rivnut: hold the bolt stationary and tighten the nut to further compress the rivnut.