Patch cables are crossover cables. You've got two options, crossover/patch for ad-hoc and straight-through for infrastructure networking. Sorry, didn't catch on that you were talking about a reverse - crossover-type coupler versus a reverse pin-out, so the coupling is just redundant.
Theory about solution... reverse the connections on one of the cables. It wouldn't change anything wiring-wise, but if there's a difference in conductivity it might.
Was playing with a diagram to make sure I was thinking correctly...

And these are cables you'd previously used to network? You know that they're both patch cables? Don't suppose you've got a multimeter or RJ45 tester handy?
I can see the network sharing being problematic with incorrectly-configured IPs or missing protocols or something, but
(I'm assuming WinXP here) it should show a connection, just have problems with file transfers or internet sharing. If it sees no connection at all, I'm still thinking cabling or bad/conflicted cards versus network settings.
Theory about solution... reverse the connections on one of the cables. It wouldn't change anything wiring-wise, but if there's a difference in conductivity it might.
Was playing with a diagram to make sure I was thinking correctly...

And these are cables you'd previously used to network? You know that they're both patch cables? Don't suppose you've got a multimeter or RJ45 tester handy?
I can see the network sharing being problematic with incorrectly-configured IPs or missing protocols or something, but
(I'm assuming WinXP here) it should show a connection, just have problems with file transfers or internet sharing. If it sees no connection at all, I'm still thinking cabling or bad/conflicted cards versus network settings.