I managed to fill up my SD card with podcasts, so Waze failed to load. It displayed a message stating its SD card requirements... but instead of going away, it remained stuck at the splash screen (with my local TV station's advertisement). After that, it remained active in the Notification Bar, and "Return to Waze" repeats the Insufficient Memory error and remains stuck at the splash screen.
The good news, though, is that Waze isn't burning up my battery, so it apparently hasn't even reached the activate-GPS code. Normally, my phone running Waze would make a good hand-warmer for anyone navigating to the North Pole.
(Disclaimer: I'm technically on the previous beta version, because my SD card is full - I couldn't download the latest! But this seems like an edge-case bug that probably isn't version-specific.)
Device specs: Samsung Galaxy S Relay 4G on T-Mobile, all-stock (not rooted).