UILabel, important info

You mention threads. Be aware that UIKit controls, such as UILabel, can only be updated from the main thread. Make sure you are only attempting to set the label's text from the main thread and then verify if you are still having issues.

EDIT due to question edit:

First, -setNeedsDisplay only tells the view it needs to redisplay the next time the screen is refreshed, it does not force a display at that time.

Second, the iPhone screen draws at about 60 hz. This means there is an update every 0.016666 or so seconds. You're trying to update much faster than that, so only about every 160th of your updates will actually be displayed.

Third, and probably most important, you don't seem to be making any threads, unless you call -startUpdateStatusThread from a background thread. Either way, once you hit -updateFrequently everything is back on the main thread. With the frequency you are scheduling that timer, you are probably overloading the CPU and making it so that the system does not have time to draw the label. So even though you are setting new text, you aren't giving it a chance to render. You need to reduce the frequency of that timer, and you probably need to rethink whatever it is you're trying to do.