The Active Directory support for the NS4300N/NS2300N has a small limitation with some special characters in the Domain Administrator Password that prevents the NN4300N/NS2300N from joining the Domain. The special characters are: #, $, % and &. ! and @ are acceptable special characters and work as expected. This issue will be resolved in SR5 Firmware which is scheduled for release in late July to early/mid August 2008. We apologize for the inconvenience this issue has caused.
In the meantime, you can work-around the issue by changing the AD Administrator Password to not use #, $, % and & special characters. Once you change the password, add the NS4300N/NS2300N to the domain, then change the password back (or create another).