D'oh! Ok, after checking my records a bit, it turns out that it was the R10+ build that had a bad file in it (32bit Mac)...

I have replaced the download archive, so if you:

• ...are currently using a Mac (32bit)
• ...are currently using the "R10.1 or later" Riptide Pro download.
• ...are having errors - like so:
  "Unable to open file /Applications/MAXON/CINEMA 4D R10/plugins/Riptide Pro/res/strings_us/dialogs/idc_listview1.str"

...then you should go download the file again (the downloaded zip file will be named "RiptidePro_v1p6_R10p1_041210.zip").

Since the problem I was thinking of did not have to do with the R11 (64bit Mac) build, I have gone ahead and added that file to the download section as well.