What could be the reason that the WPF application will bind the processor and block the application on some computers, but not others?

Question

It stands here. Added a similar question before. We have a rather large WPF application that works fine on some machines, but in other cases, suddenly one of the processor cores is tied to 100% (only one core), and the application freezes. This usually happens when the combobox (i.e. pop-up controls) is displayed on the shortcut menu or pop-up list, so we cannot debug this because the user code is not running at this time. This makes us crazy, because again on most machines it works fine, but on some it freezes.

It's strange when we run it in a virtual machine, it works fine there too! Psycho! I'm not sure what causes this, and most importantly, where to even start searching, because, as I said, no user code works.

This happens on only about 10% of our machines, but on these machines is constantly happening. All of them are clean (that is, relatively fresh OS installations, without crazy applications, etc.) and basically identical machines: similar processors, similar RAM, the same video drivers and service packs.

So, as I stated in the title, can anyone suggest possible reasons why the WPF application binds the processor and blocks the application on some computers, but not others? We are just at a standstill!

Answer 1

Found! It turns out there is a bug in .NET 4.0 regarding UI automation and changes made by MS. Here is the information and correction! (Note: even if you call MS, they will send you a link, but it will always be a broken link. I managed to track this manually.)

Note. Their article talks about the specific case that causes this behavior, but if you use Google, you will see many problems around the freezes associated with these DLLs. Recently, they promise a fix in the .NET 4.5 runtime (from an MS post on this issue.)

Here's the KB article ...
http://support.microsoft.com/kb/2484841/en-us

... and here is the actual fix.
http://archive.msdn.microsoft.com/KB2484841/Release/ProjectReleases.aspx?ReleaseId=5583

Answer 2

Crappy video driver? Pull two cars — one where this happens and where not, and start analyzing the differences. There may be equipment defects, bad video drivers, anything in this area. WPF uses a graphics processor to render, if any.

Answer 3

Since you do not seem to have enough options, I would advise creating a new project with the simplest ComboBox in the window, doing almost nothing. This should work (check :-)). Then you add functions one at a time to the ComboBox and test, for example, when you add a command, start from empty. Do it until it breaks. So you know what feature is the culprit. You did not say if everything works with software rendering.