I don't know how or why this would effect the lens/body/tube combo but didn't your Nikon have a little surgery to work on the Canon body? Just a thought - probably way off base, tho...
I just got a set of cheap tubes from Ebay (recommendation from this board) that came from China. Cost about $15 (if I remember correctly) ... took about three weeks to arrive. They work fine with my Oly's, Mamiya, Zeiss and all other alts ... as noted their is NO contacts, so no pins to tape.
My only regret is that I didn't order one in Nikon also. Since combining tubes is done via thread, I could easily let them double as an EOS - Nikon (or vice versa) adapter for tube work. As expected for little $$, they aren't a work of german engineering, but for an entry into the world of tubes to get a feel for whether or not they are your cup of tea ... it get the job done (even if a little 'thin' feeling, i.e. lightweight)
