Funny - this happened to me for the first time today. I use the CAI Utility
program (3UT152353) The download "stalled" after 38 blocks of 145. I then
got a "com port in use" message - even though I had quit palm nav. Finally
solved the problem by hitting the handy "reset" button on the back of the
Compaq Aero (with all programs off) and then tried the utility program
again. Second try worked fine.

Don't worry about your 500km flight - it's 'In there' - you just need to
extricate it.
Congratulations, BTW

Roy