Resource Probing Issue - Troubleshooting help?

[Tyrven]

I have a localized website that has been in production for sometime.
Recently, localizations for one particularly locale (zh-TW) stopped
displaying on the test application; the same locale works fine on the staging
site (which is a different IIS application on the same server).

Given that the code and application settings are the same between the two
applications, this doesn't appear to be a code issue. Since the test dll
works on staging, this doesn't appear to be a content or compilation issue.
As such, it appears that the test application cannot find the satellite
assembly and thus falls back to the resource default.

How can I trace the probing process to help identify where this is failing
specifically? Any ideas on what I can do to resolve this issue?

Here are some specific things I've tried:
1. If I copy the resource file from the test app to the staging app it
renders properly.
2. If I copy the resource file from the staging app to the test app it
doesn't work.
3. If I create a new IIS application and point to the test folder, it
doesn't work.
4. If I delete the .NET assembly cache and reboot, the problem remains.
5. If I strip the Resx/DLL down to one resource and compile this still
fails on test (but works on staging).
6. If I specify the assembly DLL specifically in the web.config file it
still fails.

Also, beta displays a compiled DLL and associated INI file in the assembly
cache, but test does not.
C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\Tempo rary ASP.NET
Files\root\[hex]\[hex]\assembly\dl2\[hex]\[guid].