There's no limit. Maybe if you posted a code snippet, someone might be able to spot something that you're not seeing?

(edit: on further research, I'm seeing a couple of references to limits between 20 and several hundred layers of indentation -- I'm not sure if the varying numbers are different versions or implementations or what, but even if it's 20, it's *way* more than anything you'd find in these problem sets, and possibly any sane software design.)