Rather than explaining it again, I will just paste my post from the mircscripts.org forum:
Kind of hard to explain, but I'll try:
I typed '$asc(A)' into the editbox of a channel, then to the right of it (with a space in between) I typed '$asc(a)'. I then proceeded to press tab for the '$asc(a)' and it evaluated to 97 as expected. I then pressed the back arrow to get to the '$asc(A)' and pressed tab, and it also evaluated to 97. Now, we all know that capital letters and their lowercase equivalents do not have the same ASCII number, heh.
This also happens with other letters like B and b, and C and c and so on, but not with mixed letters.
And I think I have come across another tabbing bug involving the channel favorites list but I cannot seem to reproduce it everytime. Once I can, I'll post it.