Explorer crashes when opening folders containing video

This question relates to recently created video clips, folders containg older clips do not crash explorer.
Reading through the posts on this subject (back in 2009/2010) seems others have experienced similar fault but via different causes. Using Canon Power Shot G9 camera and taking mainly photos but also video clip. Downloaded to computer (automatically creates a dated sub folder for each day that has something to download). On opening the folder the 'Explorer has encountered a problem and needs to close' box opens. Attempts to close the window don't work other than Alt Ctrl Del -and closing the 'not responding' prog. Older video clips captured on same camera don't do this, it has only happened in last couple of days. I assumed it was a virus (I'd transferred the clip to my daughters laptop by putting the card in the built in reader - haven't seen her since to see if she had any problems!) So I was unable to open the folder (as others said, it was during the process of creating a thumbnail on the folder the crash happens, one folder had ~30+ sub folders and the thumbs all started to populate the folders ok until it got to the recent one containing the downloaded clip) I tried to open the folder and change the view but the pc was always quicker than me and crashed before I could alter the drop down view menu. I had to use Nero disc burning software to back up the 29 folders without the video then delete the whole folder. I tried virus scan and malware scan on the card - nothing, I tried scanning the pc hard disc with same progs - nothing? In the end - as I was keen to save the video clips, I downloaded them again from the camera into a separate folder, used a DVD authoring prog to open the video without having to open the folder and then saved the video in a different folder. That worked fine, I now have a copy of the video which doesn't crash explorer. However, I tried formatting the camera card and then shooting a video clip, downloaded it to the pc - it crashed when opening the folder.
Sorry for the lengthy prose! Why does explorer cope with older clips but the new ones crash it? Is it a virus or malware do you think or some setting that has been changed on the camera/card ? Would like to resolve the issue if anyone can help.
Thanks


(erroneously loaded into 'video' forum earlier dohhh!)