"Maybe one of A or C cheated" — is this correct?

I want to express an assertion that A cheated or C cheated. Can I say:

• Maybe one of A or C cheated.
• Maybe one of A and C cheated.

Or is neither correct?

I would drop the "one of" and go for:

Maybe A or C cheated.

If it is really important to convey the idea that either of the two may have cheated, but certainly not both, you can say:

Maybe either A or C cheated.

Either in this sentence makes it clear that you do not mean both.

As hinted in the remark (thank you!), in case you have more than two options, the use of either is incorrect. In that case, you can use one of, as in

Maybe one of A, B or C has cheated.

Again, that does imply that you do not think it likely that A and B have cheated, but not C.

You could also use and in this case:

Maybe one of A, B and C has cheated.

But I think you might risk creating confusing with people that parse that phrase in a very strict way. Was it (A) that cheated, or (B and C)?

Personally, I associate or with a choice, and and with a union of options.

Since a choice is implied here, I would prefer or.

If you want to emphasize that you have a group of people (A, B and C), out of which one may have cheated, use and.

You might want to use the Oxford comma in order to avoid confusion about (B and C):

Maybe one of A, B, and C has cheated.

"Either in this sentence makes it clear that you do not mean both." I don't agree. See http://dictionary.reference.com/browse/either?s=t.

In logic there is the exclusive or - either a or b but not a and b - and this is what you were trying to make clear with your "one of" construction, but it is difficult to be precise in English, unless the context makes it clear that the (two) options are mutually exclusive as in right and left, up and down.

I am not clear how certain it was that anyone cheated in your scenario, but I would go for "one person cheated - either A or B" or "one person, either A or B, cheated". You could omit "person" but it would by stylistically odd.

You could also go for "either A or B cheated, but not both".