This issue occurs due to the presence of Cisco bug ID CSCsd44604.
The Extensible Authentication Protocol-Flexible Authentication via Secure Tunneling (EAP-FAST) Protected Access Credentials (PAC) file exported by the csutil utility on Cisco Secure ACS for Windows version 4.0 cannot be imported to the Aironet Desktop Utility (ADU) manually.
This issue is seen in these versions:
Cisco Secure ACS version 4.0(1) Build 27 on the Japanese Windows 2000 server
ADU versions 2.6 and 2.5 on the Japanese Windows XPJapanese Windows 2000