Compiler error "capture mode"

Yesterday my code worked perfectly. I didn’t change anything until now. Suddenly when I am trying to compile, I get 434 Errors, stating mostly something like this:

Error	418	error C4573: the usage of 'ASomCharacter::bCharIsMale' requires the compiler to capture 'this' but the current default capture mode does not allow it	

What could be the problem here?

The error was caused by the following for-loop:

	for (int32 iSpellList = 0; iSpellList < LearnedSpells.Num(); iSpellList++)
	{
		AllSpellsString += DisassembleSpellToString([iSpellList]);
		AllSpellsString += Delimiter;
	}

I forgot the Array-Name infront of “[iSpellList]” … but that was some confusing compiler error :-/