I got this response from WhatsApp today:
Sorry for the inconvenience. This is a known issue and we are doing our best to improve WhatsApp in a future update.
In the meantime, please downgrade to the previous version:
Go to http://www.whatsapp.com/android/2.11.23/WhatsApp.apk on your phone
Open the file that is downloaded
You may need to disable Unknown sources in your system security settings to install this version.
We apologize for the inconvenience.
So it seems something in the WhatsApp update was at fault. No issues as of yet using the 2.11.23 version.