January 11, 2010
If you have recently installed the latest Facebook app and enabled contact sync between the Facebook app and your iPhone Address Book, most likely that is the problem. The bug is not with the Facebook app but with the way our app re-sizes images for your contacts inside of your chat conversation. Obviously we are working on a fix and will submit it into Apple shortly.
To resolve the issue, try to follow these steps:
1. disable facebook sync and facebook photo sync from inside the facebook app. to do that, go into Facebook app, go into 'Friends' and tap on 'Sync' in the top right hand corner.
2. launch WhatsApp and see if step 1. alone fixed it. if it did not, try to replace your current Address Book with the a recent iTunes backup.
If WhatsApp still crashes for you when trying to have a chat with a specific contact, delete a picture for that contact from the iPhone Address Book (or to be safe delete pictures for all contacts in your Address Book with whom you use WhatsApp chats with)