Unable to authenticate

We have something called a DocSend.  It is a computer hooked up to a copier that runs an application from EFI that lets you scan a document on the copier and email it to yourself or someone else.  At first it worked fine.  Now we sometimes not all the time get authentication errors.  The software just tells us it is unable to authenticate.  The software is trying to authenticate against our active directory.  We started having trouble after we removed one of the 2 domain controllers and added a different one.  I have been checking the event logs but can't find anything that looks like it would be caused by the docsend error.  

Does anyone have an idea on what would cause intermitent authentication errors?
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Is your machine on a wireless network?
Wireless is still extremely unreliable for things like this.
The other thing would be to check your network cable if you're not on wireless.
Stacie2lAuthor Commented:
No, these computers aren't running on our wireless network.
Hi, what was the time period between adding this device and removing one of the Domain Controllers?
Is it somehow possible to disconnect this device from domain and add it back again?
Stacie2lAuthor Commented:
We found out after checking the packets from that machine that we have some problems with one of the domain controllers.  If it connected to one it was ok but if it connected to the other one it had problems.  We are getting another blade for the server and will be setting up another dedicated domain controller and remove the one that is causing problems.

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