You only need 1 of each type of zeppelin part to be able to get to Aleroth. That will give you access to a couple good traders, but before the Hall of Echoes there is not a lot to do in Aleroth, so you are still stuck at pretty much the same point.
Try emailing support@larian.com, with a description of the problem and maybe a link to this post (see the DKS
support page).
Maybe another save will help them track down the problem, or they may at least be able to remove the barrier, or something.
In XP the saves are in the folder
C:\Documents and Settings\ %username% \Local Settings\Application Data\Divinity 2\Savegames
or in Vista / Win 7
C:\Users\ %username% \AppData\Local\Divinity 2\Savegames
You may need to set Windows Explorer to show hidden files and folders (
XP, Vista,
Win 7).