[plt-scheme] Problem with require statements using PLT4.x

Hello PLT,

I have a PLT-Scheme 4.1 install on Windows XP and tried the following
expressions all prefixed with #lang scheme:
(require (planet "list.ss" ("dherman" "list.plt" 2 0)))
(require (planet "sicp.ss" ("soegaard" "sicp.plt" 2 0)))
(require (planet "pairing-heap.ss" ("wmfarr" "pairing-heap.plt" 1 0)))

None of them worked, they all return the same error ... "string->number:
expects argument of type <string>; given #f."

I have no idea what that means, could any one be of assistance

Thank you,
Joshua Ewulo
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