The assembly could not be loaded problem

[ciprian.amariei]

I was using binary serialization and deserialization in an office
addin. I had a strange problem when deserializating. I got a an
assembly not found exception, although the data serialized was from
the same domain where deserialization was called, so the assembly was
already loaded.

I found a workaround for this on a forum creating a handler for
AppDomain.AssemblyResolve Event that searches for the required
assembly in the loaded ones and returns it if found. this solved my
problem but I find this problem very strange, have any of you had the
same problem? Can anyone explain why is this happening?

Thanks in advance, I hope that this will save someone's day.