I have the 9630 running "whatsapp" on os5.0. Do you have skype on your phone? I had a problem at first getting both on my phone. If I remember correctly, I had to unistall skype, install whatsapp, then reinstall whatsapp. If you have skype, you might try uninstalling it and then installing whatsapp.
I've never installed skype and when i install whatsapp i let it edit all it needs...
this error can be due to the fact my phone is an american 9630 with verizon carrier unlocked and switched on TIM Italy carrier?
I have an american 9630 on verizion, but it is not unlocked. Sorry I could not help you, perhaps if you posted on the "blackberry apps" discussion, there is a thread entitled "official-whatsapp-messenger-support-thread"
you might find help there