Thomas,
Since Register Level Programming (RLP) is not supported by NI through traditional channels such as phone and email support, you may have more luck posting your question to the Driver Development Kit (DDK) Discussion forum instead of the Digital I/O forum. The DDK forum is the best site to discuss register-level programming applications and will get the most focus from other engineers dealing with RLP applications.
Driver Development Kit (DDK) Discussion Forum
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=8&RFORMNUMBER=3&RHIDETAG=TRUE&UCATEGORY_0=_321&UCATEGORY_S=0
Additionally, if you haven't done so already, you may want to check out the DDK. As a free download, it provides development tools and a register-level program
ming interface for NI data acquisition hardware. The DDK is designed to make RLP easier for customers.
Measurement Hardware Driver Development Kit (DDK)
http://sine.ni.com/apps/we/nioc.vp?cid=11737〈=US
Regards,
Justin