XnView: MP 1.6.1 - 64 bit
OS: Windows 7 Professional 64bit
I just upgraded from 1.4.4 to 1.6.1 and was confused that I couldn't browse archives anymore.
Effect: archives get instead just opened with the associated program.
To reproduce:
1. unpack "XnView 1.6.1 win x64" from the .zip
2. try to open any archive
Actual behaviour (bug): 7zip gets opened. (associated app for archives)

A somewhat related bug is that even /if/ browsing archives works, right clicking archives will keep "Open" greyed out anyways.
Expected behaviour: XnView browses the archive.
What I've found out after literally mix 'n matching versions 1.4.4, 1.4.5, 1.5.5 and 1.6.1 I've been able to "fix" the problem by just using the "archive.dll" of 1.5.5
That literally makes it work again while using everything else that comes with 1.6.1
The dll in 1.6.1 is also ~200 kb smaller, maybe something's wrong with it?
I'm also aware that since I am on Win 7, this might be an issue exclusively to Win 7, and if that should be the case, nevermind this issue.
But I wanted to mention it anyways, in case it's something further reaching.