I am faced with the following issue and at this point I feel like I'm severely lacking some sort of tool, I just don't know what that tool is, or what exactly it should be doing.

Here is the setup: I have a 3rd party DLL that has to be registered in GAC. This all works fine and good on pretty much every machine our software was deployed on before. But now we got 2 machines, seemingly identical to the ones we know work (they are cloned from the same image and stuffed with the same hardware, so pretty much the only difference is software settings, over which I went over and over, and they seem fine).

Now the problem, the DLL in GAC takes a very long time to load. At least I believe this is the issue, what I can say definitively is that instantiating a single class from that DLL is the slow part. Once it is loaded, thing fly as they always have. But while on known-good machines the DLL loads so fast that a timestamp in the log doesn't even change, on these 2 machines it take over 1min to load.

Knowns: I have no access to the source, so I can't debug through the DLL. Our app is the only one that uses it (so shouldn't be simultaneous access issues). There is only one version of this DLL in existance, so it shouldn't be a matter of version conflict. The GAC reference is being used (if I uninstall the DLL from GAC, an exception will be thrown about the missing GAC reference).

Could someone with a greater skill in debug-fu suggest what I can do to track down the root cause of this issue?