you must have entered or written something down wrong. Without explaining how the system works, the only way it would fail, is if something is entered wrong. If I explained the whole system, someone with too much time could hack it. In fact, there is a slim chance, if you spam the right sequence of numbers and letters, you could get 8 billion EXP.
However, I have ran into the problem a few times, and I will agree that a handful of the letters look the same.
To clarify, i believe numbers show up in yellow, and all letters are in caps. So, an I might look like an L, 0's and O's, and i have had troubled with B and 8 on a couple occasions.
type -save a few times, so the letters dont get covered up by spamming players, and make sure you write it down correctly.
If I was smart, I would remove I, L, 0, O, 8, and B, but alas, I cant >< so I can only advise to be careful when writing it down, and try not to lose codes.
