Is SC 6.4.5 compatible with Cisco UCS 2.2(8c)?
I've found this PDF http://en.community.dell.com/dell-groups/dtcmedia/m/mediagallery/20438558 See page 76.
SC 6.4.5 is not listed.
It just means that the version of SCOS that you are using has not been certified. Does not mean it would not work, just not certified.
You can also just upgrade your version of SCOS to the latest revision for full support.