Of course u should be able to call it in cash. When someone takes forever every hand why should they waste my time messing about or tanking when they nearly always fold but don't want to? It's even worse if it's a timecharge game.
That's not when the clock is usually called though, is it? Like in the situation I mentioned above, I had a big decision on one hand - and it was the player who was holding the play up every hand who called the clock on me. Isn't that usually the case?
Also, it was a cash game at DTD - so not timecharged.