So perhaps the culprit is not which addon, but when. I will continue to use this approach until I encounter this problem again.
We have a confirmed issue with the GoFlight modules. They work together with our modules only if you load them manually after FSX started. So, maybe this is your issue, or another product is behaving the same.
With regard with the GoFlight module, I *think* the main issue is that they compiled using the VS2010 ( or VS2012, not entirely sure ) compiler, so they are getting a dependency on the VC++ 2010/2012 runtimes. But also, as any FSX addon that is also a Simconnect client, they also get a dependency on the VS2005 runtimes, because they brought the Simconnect library too.
This issue is not very well known amongst developers, but according to the very long and complex explanation on this site:
http://siomsystems.com/mixing-visual-studio-versions/Having dependencies on multiple versions of the VC++ CRT runtimes in the same program IS asking for trouble.
Which is why, all our modules are still compiled using VC++ 2005, so they are only dependent by ONE runtime, the 2005 version, which is the same used by FSX and Simconnect.
The loading order CAN affect this, because the way the (very complex) Windows side-by-side loading system works, it's supposed to TRY to allow multiple versions of the same .DLLs running together in memory, and this will work or not, depending on the loading order of modules.
Not sure if you have the Goflight modules, but perhaps the same issue is valid for other modules too, I see that many developers use different versions of the VC++ libraries quite liberally, without worrying so much of the potential issues when running together.