I just installed Poser 7 on my Mac running OS 10.5.5. After purchasing content to download from Renderosity the folders download as unzipped folders. I have Stuffit Expander and it doesn't have the option to automatically unzip files-I already checked. Other vendor's content downloads unzipped without a problem. As a result, I haveto manually transfer the files/folders into Poser. I'm not sure I did this correctly or why I should haveto. I emailed the vendor of one of the content material and he's at a loss as well.  Why is this happening? Could someone on a mac please tell me what needs to be done?  

Is it possibly that when downloading you used an "open with"  option rather than simply download the file to disk ?  I dont know anything about macs though, just a thought.
 

 I just click on the download content in my account and it automatically downloads to my computer and unzips. Should I control-click and use the "save linked file as.."? What other options are there?

I'm on an a Mac with OS X Tiger, and this is what I do... it works fine for me, quick and easy.

Download as normal, and it automatically unzips, usually into a Runtime folder, sometimes into a product-name folder with a Runtime sub-folder. I always make sure there is a top-level folder with the product name, containing one Runtime and one ReadMe folder. At this stage, I take a copy of the complete product package onto an external drive.

To install the product Runtime into my Library Runtime, I use a little OS X utility called dittoGUI. You can get it for free, or pay around $8 or so to remove the "gimme some dosh, please" image.

With dittoGUI open, you just drag the source Runtime folder onto the Source box, drag the destination Runtime folder onto the Destination box, then press the Ditto button, and everything is copied into the correct place.

Often there are multiple download files for a single product. I also use dittoGUI to merge these into one Runtime before making my backup copy.

Hope this gives some useful ideas, even if you don't want to do it this way.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)

 Check in the trash the zips are probably sitting there.

I also use PHILC's Unzip free utility

 the zips are in the trash but when clicked on they "unarchive" into a folder again. What's the best way to unzip it directly into Poser without having to manually transfer the files?

 I downloaded ditto and tried it out. It seemed to work on a test folder. I've already manually installed the downloaded content.

 http://www.philc.net/unzip.htm

try unzip by PhilC

It may be a setting option in your browser, or Finder that is automaticly uncompressing the downloads. (I've seen such options in my Macs; but always disable them.) (:

 Where where I check browser settings option?  This problem only happens with 2 content vendors. This problem doesn't happen otherwise, so it shouldn't be a settings problem. Perhaps a problem with my Mac Pro computer?