I have 2 Flirc's, both with the same issue. They have been running along fine for a while now, no firmware upgrades in quite some time. I want to take advantage of some of the improvements in XBMC control and also add the harmony profile so I went to upgrade today, but both cycle through saying "Could not upgrade firmware, contact support" when I try to do so in the 1.2.6 gui. It seems to crash frequently while trying this as well. This is the same on a laptop running Win7 x86 and on a desktop running Win7 x64, both with fresh program installs.
I would try to do the upgrade via command line but can't since I don't have access to the bin file that is bundled in the gui. I did check the current version there and it says "Bootloader 10.5". Let me know what I can do or what other information I can send you to get this figured out.
Thanks!