its not only the .png files, look at the date on this one http://forums.adobe.com/thread/418917?tstart=0
The problem is the server's virus scanner. This is a known problem and they are working on fixing it. In the meanwhile, use the "camera" button to upload pictures instead of attaching them
Is there some reason why images put up via the camera icon are bound to be safe, but attached ones might be dangerous? I can see scanning some types of files, but images??? I'm sure my ignorance is showing here, fill your boots
i prefer sandals
All the files that you attach are scanned for viruses but don't ask me why as it seems quite pointless to me. If i remember correctly JC said during the preview that they are looking into the issue with the long queue time, that's all i know about this subject.
by the way, there actually are viruses that can infect pictures but their number is incredibly low