It's worth checking which version you have installed - if in doubt, always grab the latest from whatsapp.com on the phone. And yes, I really, really wish the Whatsapp folks would put in some kind of auto-updater into the client - there's really no need for the sort of confusion above.
Whatsapp changes force update for Symbian client
Published by Steve Litchfield at
Whatsapp, the incredibly popular cross-platform instant messaging client, may have been silent for you for a few days. Don't worry, there's a good reason for this - for technical reasons it seems that the Whatsapp client sometimes declares itself obsolete - see the screenshot below! It's unfortunate that the client itself couldn't tell you it wasn't working anymore, or even auto-update itself, but rest assured that there's a new version of Whatsapp up for download now and all's well again.