Hello All, I recently downloaded the Nuvi 660 firmware upgrade from the Garmin site to upgrade to v2.70.

I did this as I read some other comments that the Garmin webupdater application has (in some cases) caused corruption.

Updating garmin nuvi 350 updating multiple values

I just updated my Nuvi 660 from v.3.5 to v3.6 software and got the error message. Your procedure worked great,had the "System software missing" after a Webupdate_241.

Yes, it took at least 60sec for pre boot mode to disappear but once it did, unit was back to normal with v3.6 OS. I was on Wi Fi late at night with very good speed,it all took only about 5 minutes.

When I tried to do it again, I got the message that the 670 was already updated,tried to update again,got the message"The update file is corrupted".

I hope this assists other if they encounter this problem. Strangely when it came back up the v2.7 upgrade had worked for me too.

I still don't know why the firmware upgrade process failed BUT after performing the above sequence I found that the firmware upgrade had actually worked (strange). Had the "system software missing" problem after attempting to upgrade software to v2.7 using the web updater. JW hi nick, thanks from me as well for your accurate and useful post - was having kittens thinking i'd d**yed up my brand new garmin nuvi 310, but your instructions have saved the day.

DON'T USE WEBUPDATE to update the device is all i can say...

go to the direct software update link: - Download: Nuvi 660 software update version 4.70 (4.86 MB) as of December 11, 2008 Thank you, thank you for sharing the info on holding power button down.

When the unit came back up again the following error came up on the screen: "system software missing" The Nuvi would not boot! HOLD down the power button and you will see "Pre Boot Mode" appear on the lower part of the display.

I contacted the local Garmin support rep and I was given the following sequence to recover from this condition: 1. KEEP HOLDING the power button down and the display will flicker, do this until the pre boot mode message disappears.

This seems to take a long time (60 seconds at least). Once the pre boot mode message disappears release the power button and your device will perform some activities to recover from the above problem.

Apparently this sequence will only work with the above error.