Hi nunndaddy,
Does your client get the same issue on our demo below?
http://www.ajaxuploader.com/Demo/select-multiple-files-upload.aspx?UploaderDebug=1
QueryString "UploaderDebug=1" will open the debug mode, and you can see the debug info at top-right.
Please show me the info if your client get the same issue on that page.
And please let your client disable all antivirus, firewall and pugins(google toolbar Etc.) of the browser except silverlight/flash to try again.
Keep me posted.
Regards,
ken