I also own an Oregon 550 - the current firmware on this unit says version 6.40 (where the Oregon 6x0 says version 3.70 or below).
So I guess that even though the Oregon units 600 and Oregon units 550 shares the same name "Oregon", looks and feel identical in the software, it is for real two different firmwares! Correct?
Will the Oregon 550 firmware update also be affected in the same way as Oregon 6x0 and Montana units have been? As far as I can see, the version 6.40 is the lastest version (from august 2013), but I am not sure if there is a newer version than 6.40 for my Oregon 550, but I am afraid that will be affected also, if updating to a higher firmware version.
Can anyone confirm, that the older Oregon 5xx and 4xx are not affected!?