The issue seems limited to the nuvi 7x5 models, and may be related to a bug in the MTK chipset used on those units, but that's all speculation at this point. What is known is that apparently there's no easy fix, and if you're affected by this bug you'll probably end up having to send in your unit to Garmin for a replacement.

So far people are generally saying Garmin Support is doing the right thing, offering free replacements for any bricked devices.

I personally own (and use every day) a Garmin nuvi 765T, and have the most current maps and firmware installed, and have not experienced any problems. Is your nuvi 7x5 still working?