Well, on most systems that I've ever seen (apart from military ones) the BIOS password is an alpha-numeric of EIGHT characters [u]or less[/u] [usually at least five characters].
Distinctly these BIOSes dislike the usage of combined upper and lower case characters in the password.
[b]"i Guess"[/b] contravenes BOTH criteria it is not 'eight characters in length' and it 'contains upper and lower case' characters.
Try it in all one typeface, try it with an extra space at the end, try it with one character less by removing the space between the first two characters, try it with some other combination that has so far defeated me.
Good password by the way - it defeated you! ;)
Edited repeatedly due to errant wireless keyboard!