Under Linux you generally don't want an virtual CD to pop up every time you connect your modem - especially as with 2.6.32 the 3GU finally made it into the option driver!

To get rid of the pesky virtual CD every time you plug in your A-LINK 3GU you can simply put it in "Test mode".
Haven't noticed any adverse effects. This mode is used to enable the connection of diagnostic software on the else unused serial port. It so happens to deactivate the CD feature, so hey we'll use that:

AT+CSWITCHTEST=1

Voila you're gold!
You might need to put your device into regular operation mode after it has rebooted by issuing:

AT+CFUN=1

In general the AT-command reference published by A-Link can't be described as anything else than outdated and incomplete rubbish (at time of writing this, hope dies last y'know). See the other text files for more info.