It's in the variable OK, it just isn't displaying very well.

Try setting ASCII on. See the following test script:
 Code:
Break ON
$=SetOption("ASCII","ON")

Function DecodePass($PASS)
	Dim $i
	For $i=1 To Len($PASS)
		"	'"+SubStr($Pass,$i,1)+"' = "+Asc(SubStr($PASS,$i))+@CRLF
	Next
EndFunction

Dim $Pass

"Enter Password: " GetS $PASS
While $PASS
	"Password is:"+@CRLF
	DecodePass($PASS)
	@CRLF+"Enter Password: " GetS $PASS
Loop