A Google search of "Quicktime Problem" +PC returned only 684 hits... many of which are duplicates or links down a thread on the same issue. That hardly seems to be a pervasive problem. changing the word "problem" to "problems" only increased the hits to 1200.
I suspect you have a software/hardware incompatiblility where Quicktime on your system is clashing with either hardware on your system or some other piece of software is not releasing a system resource so that Quicktime can use it. In the past there have been known issues of conflicts with RealPlayer and its components.
Most issues with Quicktime on PCs were caused by an incomplete or failed initial installation. Try removing it completely and then re-installing it with the latest version.
It doesn't matter what the conflict is. it causes problems. If I have to remove another program to run a Quicktime clip, it is of no use to me. The point is, there are known conflicts.