Strange that F5 production FW is still at 4.10 and the beta is now at 5.09.
Also strange that the beta version jumped to 5.x without major new features.
Anyone know what's going on?
If it's not available (yet) via Garmin Express nor OTA, you can always try Garmin WebUpdater which is almost always available immediately. I just checked and 5.10 wasn't available for me via Garmin Express or OTA but I was given the option to update on WebUpdater. And the nice thing about WebUpdater is you can also force a re-install of the current version or install other updates (such as language files).
You can download WebUpdater on Garmin's site at: http://www8.garmin.com/products/webupdater/howtoinstall.jsp
Cheers,
Douglas