Hello, lately I have been experiencing this weird thing happening to my bitcomet downloaded files. FILE EXTENSIONS ARE MISSING ! But I do make some wild guesses and perform some heat and trial methods to figure out the extensions and add them to the files and eventually able to work with them. I just open the torrent via BitComet and won’t change anything on the file/folder names. I just click the Download now button and wait before it is done. When I go to check the files most of the time extensions are missing. Then I try to add .pdf, .rar, .zip and work with them accordingly and find the files are intact and good to work with. I have also updated BitComet to the latest version available. Thanks. 
If you’re using magnet links, try downloading the torrent files instead.
Queenie, can you inquire if there has been any progress with this problem? We’ve been getting reports of this for over a year now. When users open torrents from magnet links and start the torrent immediately it will download all the files without extensions. Last year kluelos was able to verify that if you wait a few seconds before clicking the download now button it will work properly, but we’ve continued to get these reports so it really should be fixed.
I have found the same problem and it appears as you said Usual Suspect to be linked with downloading using magnetic links. This was not a problem with earlier versions of BitComet. I hope it can be fixed in future versions. I am having problems with my version of BitComet downloading torrent file so have to use magnetic links.
This problem is supposed to be fixed in next version soon.
If you read in the forum you’ll notice that one of our staff members was able to determine the problem occurs when you start the download before bitcomet finishes getting the torrent from the magnet links. I tried many times to reproduce the error but was unable, but by waiting a few seconds to allow the process to work you should be able to avoid this.
I suspect this issue occurs more often on slower internet connections or ones that are “busy” when quarrying the file names is occurring.
All this info has been posted in the forum at least a dozen times and could have been found in a manner of seconds by doing a search.
ps. Thank you for the update Queeniequ, it will be nice to have this minor bug finally fixed.
I was assuming this was not fixed because I clicked on help>check for updates and I was told I am running the most current version, however i KNOW i was not as I just saw that v1.40 and I was running v1.35 !!!
So if this is still not working for anyone, you might try a manual d/l of a new version!
thanks for the bug fix!