Viagra et al - aren't they great??

[Abracadabra]

Coffee is fine with or without milk. Could be those other factors you mentioned, or lack of energy / hydration (gotta eat something, preferably sweet, easy to digest, contains fluids, no fat), the girl wasn't really to your liking, or even your own libido.

Yep, my garmin told me I was running on empty..

Incidentally, what do you eat prior :
"preferably sweet, easy to digest, contains fluids, no fat" ?