Fonts, fonts and fonts again...
Illustrator was originally developed by the Adobe guys not as a useful application, but as a demo as to what one could do with their wonderful (new at that time) PostScript language.
After tourinmg and demoing 'Illustrator' - people began finding practical uses for it.
This being the reason why Illustrator - still today - behaves pretty much like the syntax in the PS language - and the reason why Illustrator is 'sensitive' to deviations from the PS standard.
(Before ATM DeLuxe we were some, that used Illustrator as a 'font-checking' app, as a couple of words written in Illustrator in the suspect font, would make Illustrator go down with a loud crash within a few operations to those words).
All this only to explain to that you could try to temp. remove your font folder and then try. If Illu starts up OK - you have the tedious task of findeing the guilty font (-s)
Happy hunting
John Philip