I had similar problems with an early 16GB Transcend card in my Edirols 4 or 5 years ago which I think didn't conform to the SDHC standard and was weary of trying their newer ones too. But I tried a newer 32 GB class 10 Transcend card with no problems and now have 4 of them which have been working perfectly in all my Edirol and Tascam recorders for over a year (R09, R44, DR2d, DR-680). I'm now a converted former Transcend critic.
Edit- I just did 8 channels on the DR-680 and four more on the R-44 to the Trancends @24/48 last night.