Please consider moving this question as-is (no need to recreate) to the proper forum for maximum visibility. Questions written to the users' own "Discussions" space don't get the same amount of attention and can go unanswered for a long time.
You can do so by selecting "Move" under ACTIONS along the upper-right. Then search for and select: "Celerra Support Forum".
Please wait for others that have experience with this; however, thinking out loud a bit about some details that people may ask:
1) Can I assume it is from Windows 2003 to Windows 2008?
2) Also what version of DART OE?
The Dart code 22.214.171.124 totally support windows 2008. Some bug has been fixed in the version 126.96.36.199, such as it has been fixed to deny creation of files based on file filtering rules for Windows7/ Windows 2008 clients, and meanwhile 188.8.131.52 use correct CIFS-based SPN to access Domain Controller. For more information, I would recommend you to refer the release notes.
In DART 184.108.40.206 and lower, EMC has fixed some bugs, such as Data Mover panicked when a Windows 7 client connected to a CIFS share through a Riverbed WAN accelerator with the SMB2 protocol enabled. However, there are still some bugs has fixed in the DART 220.127.116.11 or higher, such as the Data Mover panicked when an application made a very large number of accesses to the same file from many different Windows Vista and Windows 7 SMB2 clients that used SMB2 file lock request operations. So I suggest you can upgrade the NAS code to higher.