Forms: Recipients get varied error messages when submitting

Where do I start troubleshooting? - see last paragraph

I created a form with Acrobat 9, enabled usage rights, and distributed it through the Distribution and Tracking Wizard (selected “Automatically collect responses on my own internal server”). Told the 42 recipients to be sure they were using Reader 9 to read and submit the doc.

Six recipients got this message:
The data collection workflow has ended and data is no longer being accepted. Please contact the initiator with any questions.

Three recipients got this message:
Acrobat could not submit your data. Please see Tracker for more information.

Two recipients got this message:
This completed form is returned to you through email because the recipient does not have Acrobat 9 or Acrobat Reader 9 (or later version) This is not the case!

One recipient got a message saying that the initiator's box was full and another recipient got a message saying “Could not access the network resource”

Curiously, the two recipients that submitted their response with Reader 8 came through fine.

One variable that may have an effect is that the network folder where the responses were going was restricted to only three people (whose responses went through). Since then, we have taken off the restriction. But the recipients still cannot submit their responses.

Thanks
Leah