I am sharing with others who may have or might in the future experience tons of frustrations with updating the ROM of the HP49G+ using an SD card.
I had a 64MB SD card by Lexar that was in an early s/n 49G+. I decided to install the latest ROM version. I also opened a new 49G+ with a CNA452xxx s/n. What happened next happened to BOTH machines and drove me nuts.
I copied the ROM update file to the SD card and followed the procedure. The steps went well until I came to the last step in which I reset the calculator. Rather than seeing the stack as expected, the calculator took me back to the ROM update choice menu (1 USB and 2 CARD). I repeated this process many many times on EACH calculator without escaping the update menu after I pressed RESET. I searched this web site and that of HP for instructions. All were saying the same thing (last step is to press RESET). I even tried varying the duration of pressing RESET--nothing worked.
I tried to use the connetivity software but it was not as smooth as TI's version (it did work ok later). I finnaly decided to use a San Disk 128MB SD card. When I repeated the procedure on each calculator everything went smooth. Now both 49G+ have the new ROM.
So if you are suing some SD card to update the ROM of the 49G+ and experience similar issues. Ditch that SD card and use another brand.
Namir