i have the same problem. i noticed that when the trip computer doesn't work the track log doesn't save the track either when the unit is shut off. i've tried different length of startup time and can't find any pattern. sometimes it recrods and sometimes it doesn't (i have it set to recrod every track) and when it doesn't record it appears the trip computer isn't working either.
As far as I can tell its a problem with the igo application itself. I noticed in the last EU update that there was a reference in there to making an "improvement in track log recording". I am hoping that this is a patch that is coming for all units.
i've noticed that several times track log recording worked if the car has been moved a short distance before the system is fully booted up. meaning if i stop to get gas, shut the car off, get gas, start the car and move it a few feet to go into the gas station not waiting for the system to boot up, shut it off, start it and wait for it to fully boot up to move then track loging and trip computer both work.
now if i skip the step with going into the convenience store then they don't work.
i haven't tested this enough to say that that's how it is every time. but i did notice this behavior a couple of times.
almost appears that there's a correlation between track logging working or not working if the last recorded and starting gps locations are the same/different. or maybe it all depends on the order in which things get loaded. i.e. track loging starts and checks for gps signal, no signal = no logging and no retry to check for signal again in a few seconds.