I’ve owned a Marantz PMD661 for a while now and I was quite bummed to find I could not use any of my SanDisk 8GB SDHC Class 4 cards at the time (about a year ago).
I tried many things at the time, I formatted the SDHC Card in the Marantz PMD661, which worked, but when I went to record audio, I would get a “Err Card 2” message when I tried to record (or it would error on booting the recorder).
The only solution, buy more 2GB SD Cards to use. Lately I have seen less and less of them in the stores, so I also recently did a last time buy of about 5 of them figuring that many would allow me to use my recorder for years to come (yes, these flash storage devices do wear out).
Well, it looks like Marantz/D&M Professional finally fixed the SDHC issue for most of the cards out there. On 6/17/2011 they released a new firmware version (A2.03), the last update I had seen on the website was A1.17. The firmware update was mostly to address the use of larger capacity SDHC cards.
I installed the new firmware per their instructions (used a 2GB card) and now I can successfully record audio using the SanDisk 8GB SDHC Class 4 cards I’ve had for a while now. With the 2GB cards, I could record a little over 3 hours of 2 channel audio (cd quality – PCM-16bit, Stereo, 44.1 khz), with the new 8GB cards I can now record over 12.5 hours of audio as seen on this picture to the right (not sure I’ll ever need that much recording time).
Thanks Marantz/D&M Pro for the update!
– Dom
Dominic Pruitt 
i hav accidentally open the cabinet of the pmd 661 marantz,since then no cards are being detected,so do i require installing the new firmware or is their any other software to be install,plz help
I would get Marantz support involved if no cards are being detected at all.