I've searched the Forum but haven't found anyone this exact problem so far... Trying to Import Users Into This Group: via  .csv file, and keep getting either:
  error 3
or
  Import Operation Complete
  Lines Processed 1
  Errors Encountered 0
  Records Added 0

This first happens when I try to import following the directions. The second is the result of Exporting Users to CSV, then deleting the User and attempting to Reimport (hoping that the format of the Export would match the Import). I've tried removing portions of the data (e.g. - userid, createdate, etc), and keep getting errors. No create or expire date results in the error 3 as well.

Is this an issue of Permissions? Something else I've overlooked? We've had this issue on another install as well, but on that one we simple added things by hand - the record set was small.

Here's the relevant site specs:
CMSMS 1.6.6
FEU 1.6.11
Current PHP Version 5.2.12

UPDATE: Microsoft is EVIL!!! (at least on a Mac...)
Turns out to be an issue with the way Microsoft Excel formats .csv files on a Mac. To get around this I saved them as 'Windows Comma Separated (.csv)", and viola! Everything worked. Seems the CMS needs the quote marks around certain fields, and my Mac version was stripping them.

OK, it was almost that easy. One small glitch - it seems that the Expiry date is needed. When I left that to the system, it put it in as all 0's, which led the system to believe my user was Expired. Easy to get around, one you know about it. Just put in the Expiry Date in the correct format (e.g. - 02/08/2010  11:20:00 AM) and it works.

Now I don't have to enter 100's of entries by hand, or try something desperate like adding them with NaviCat!