Well, here it is 3 months later and we now can come up for a breath. Vista is a real piece of work. We wasted 4 months trying to make Hoster work on it. We MAY now have an answer, but..............
We have tried to re-create your problem; i.e. the first file in a folder being a ZIP, but have not failed once.
I called and you so graciously are going to provide us with example ZIP and RAR files.
Once we have example files, I'm sure we can naiil down what the problem is.
Currently we do not support the .rar extension, but will consider it in the future. Right now, we have a short window before we are back on Hoster and want to get some new changes and features into Microstudio.