I suspect this is not the fault of GroupOffice or Z-push, however it is very annoying.
On HTC Android phones we can select contacts as "Favourites", and they show up in a special widget on the phone. When syncing with GO the following happens:
If a contact has been added as a "Favourite" on the phone, the Comment field in GO gets overwritten with the text:
This is very annoying since any information in the Comment tab gets lost when adding the contact to favourites....