Hi again,
  as previously indicated by Alain Knaff, the ACX100
chipset support is
 finally working. I am typing this using it, with a DLink DWL-650+,
 including WEP, with the driver version 0.2.0-pre7_plus_fixes_1, on
 an older 2.4.23 kernel.
 I'll try some more @home with the PCI version (DWL-520+), and with
 a 2.6 kernel. 
More success on kernel 2.6.0 with the acx100-0.2.0pre7_plus_fixes_7.
I'll test the PCI version (DWL-520+) sometime later...
Greets Eric