Access is denied exception when loading an assembly from custom data processing extension

Hello,
I have been banging my head against this for the better part of today.
Here's the scenario. I have a custom data processing extension which
tries to make calls into another .NET assembly. As soon as this second
assembly is loaded, an "Access is denied: name_of_the_assembly"
System.Exception is thrown. I can't even catch this error as it seems
to occur on the assembly load and not on the first function call. Both
my data processing extension and second assembly have strong names and
are signed with the same key.
The rssvrpolicy.config is setup to allow FullTrust to my data
processing extension and second assembly. I have tried both URL
Membership Condtion as well as StrongName. Note that my custom data
processing extension works just fine if it doesn't call the second
assembly. Rolling everything back into a single assembly is not really
an option though.
OS: Windows Server 2003
Reporting Services SP1
IIS AppDomain Identity: NetworkService
Any ideas? Help please.
~JeffOk, I'm an idiot. It turns out that my data processing extension was
NOT signed but my second assembly was meaning that I had an untrusted
caller trying to call a trusted assembly and bomb! I went ahead and
signed everything and gave the proper StrongName membership in the
policy config and I'm good now.
I'm glad it turned out to be my problem because I couldn't figure out
for the life of me what I was doing wrong in regards to RS.
Hope this helps somebody else.
~Jeff