No, that's not right. The expansion packs were used in making Union Cove, but not having them won't prevent you being able to use the town. It just means the items from those expansions will be replaced by something else and you won't have the game play from those expansions.
Union Cove is a large town and is very graphics heavy. Not everyone can run it successfully. How far are you getting in the load before your computer gives you that message? Also, I've had times where I got that message, but I just ignore it and the game will start back loading again. So, maybe just let it go for a little while and see if it will finish even after giving you that message.
The last thing that comes to mind is whether you have a powerful enough graphics card. If not, it could cause problems with Union Cove. Have you checked the game specifications against your computer?
@Anushka: Am I right about this?