An exact copy of a working LaTeX code doesn't work!? OK, someone needs to explain this to me, because my head is about to explode. Forum member Jorriss has a LaTeX code in his signature. It includes the LaTeX code \Psi in two places. The second one is displayed correctly. The first one isn't. My first thought was that this has to be the 50 character bug, but that didn't seem possible, since there wasn't enough stuff before the first \Psi. I got curious, so I did a right-click, "show math as", "TeX commands", and copied the LaTeX code. I typed four dollar signs in the quick reply box, pasted the LaTeX code in the middle, and did a preview. The first \Psi was still messed up. Then I typed the exact same code below the code that doesn't work, and this time it worked. So now I thought OK, Jorriss must have done something funny here on purpose. Maybe the character that looks like an i isn't really an i, or something like that. So I deleted the character that looked like an i, typed an i, and previewed. It still didn't work. OK, so it's not the i. Then I repeated the procedure with the s, and then the P, and then the \, and it still didn't work!!! I had replaced all the characters, and it still didn't work. $$\Psi$$ $$\Psi$$ I have made one observation that may be relevant. My FireFox underlines "si" in the first \Psi, as if it's misspelled, and doesn't underline "si" in any of the other Psis in this post.