I have adopted a work around to solve (my) problem.
I don't trust Mustek nor Apple to find a solution any time soon, or later.
I'm using a virtual machine created with Parallels Desktop 4. VMWare can be used too.
I use the virtual machine as a "layer" that supports a scanner application. I mean, with Windows 7 running, optimized for speed, set with a large virtual memory and the strictly necessary programs running in the background.
The virtual machine itself was optimized accordingly with my MacMini.
Once I got this light and fast machine and a fast and light Windows 7, I installed "Vuescan", and (among other preferences), I set it to save the scanned files in the Mac Desktop.
It runs and scans even faster that in the previous OS X Leopard, when ironically the scanner drivers ran natively in the Mac and with Photoshop CS3 and CS4 (for MAC)
Here you have some shots of my configuration:
Parallels machine menu: The scanner-machine in suspend mode for faster start:
http://img.skitch.com/20091031-geqkrjwakfjnusxw7w6k73p5qm.jpg
The machine selected and ready to start:
http://img.skitch.com/20091031-gkkpwsaia7a7axu3e2g7tq8rsw.jpg
The (application) started maximized in the machine, so it looks like the application running by itself on the Mac desktop:
http://img.skitch.com/20091031-fx6fafedcicj54iqgjx3gjsgpq.jpg
Making a preview with the scanner:
http://img.skitch.com/20091031-bia7w5pucb9rfx7isjsbg5dwwq.jpg
Scanning the selection field:
http://img.skitch.com/20091031-8t3ngftuyyas526a2ugybfypga.jpg
Setting up the default "Save" folder:
http://img.skitch.com/20091031-rk6ekhjcygkbkd8y8up3kg3hdj.jpg
File saved conveniently on my desktop, so I don't have the go for it through the virtual machine and do additional steps like drag 'n drop or copy and paste:
http://img.skitch.com/20091031-j7bs7pxuaftcpxx3finx428tx3.jpg
This can be made using Windows XP, Vista and any other application for scanning, i.e. Photoshop.
I will stick with this solution until I can!