I've had ALL trade trucks disappear too once starting to supply a GW. Not just the trucks that visit the GW, but every single one in my city. And even before this happened imports just sat in depots not being transfered to empty buildings that desperately needed them. I've found having more than one trade depot/port starts to cause some problems, though having one limits the materials you can import/export.
I too believe this game will become great if it's fixed. So far every city I've started has died because of some bug, mostly due to the loss of all trade trucks or the "no shops, no shoppers" problem. The latter I put down to bad traffic, whereby sims are unable to locate the shops next to them, which are closing because they have no business.
And the map size...it's so depressingly small I want to cry!