Yes, each new version of LabVIEW only carries the capability to save
for one version previous. So, you would need to save the 6.1 VIs for
vesion 6.0, and then from LabVIEW 6.0 save for 5.1. If there aren't
too many VIs, one of our engineers here would most likely have no
problem with making the conversion for you. You could email NI with
them to make it more private, if you'd like, rather than posting them
on the site. (To create an email request, go to www.ni.com/ask).
Hope this helps!