@water, You are AWESOME, thank you! The offender was indeed an Addon - WatchDox - a document protection Addon (highly annoying one and I only had to install it as some certification material I was studying required it). As soon as I removed the WatchDox Addon, Excel started closing properly! Woo Hoo! P.S. I've reported the issue to the Watchdox team @ Blackberry. Hopefully they will investigate and fix their Addon.