So I updated from v1.04 to 1.05, and now all my torrent tasks are gone.
I'm using Vista and I can only assume this is a User Account/folder address problem concerning wherever the data regarding the tasks is stored.
Naturally, all the downloaded files are still there and ready to be resumed.
Please don't suggest stuff like to redownload the torrent files and hash check ALL of them, cause that'd just be a pain in the @ss and surely there are better solutions.
-> UPDATED <-
I posted the message above like a year ago and would like to share my experience and possible solutions with those who may have similar problems. If you simply leech of torrents and don't really care for seeding or keeping an extensive torrent list, then skip to section II.c below. If you do care, then explore some possible recovery solutions. The entire point of this post is to avoid having to unnecessarily hash check all your torrents. Note that directories and solutions listed here are for Windows Vista as I believe this OS has the most problems.
I. PROBLEM
Okay, so I've figured this out for a while now and just wanted anyone who had similar problems to be aware. Sometimes (on Vista) installing a new version of Bitcomet resets the torrent list as well. This list is written as an XML file (Downloads.xml) which keeps track of active torrents, their hash codes, download percentage, and the like.
Now, depending on whether User Account Control (UAC) is enabled or not Bitcomet will place this file as well as other torrent-specific files (such as torrent folder where your past torrents are kept) in two places:
1) C:\Users\<yourprofilename>\AppData\Local\VirtualStore\Program Files\BitComet,
2) Bitcomet installation folder.
Problems are usually experienced when BitComet is recoded to search in one of these two destinations when it previously used the other. In this case, there may still be hope for complete recovery of your task list. Sadly other times, the list is replaced with the default empty list and all info and hashcodes within are been deleted.
II. SOME SOLUTIONS
a) To resolve this problem, the easiest solution is to disable UAC in case Vista has stubbornly reactivated it again. In some cases this works since Bitcomet tries to look for the task list in the right place again. If not, then you might be able to transplant another task list to the currently used directory (read next).
b) Bad news is that when you update Bitcomet it may delete the main torrent list (mentioned above). If you're lucky, it may have just changed where it's searching for the task list. Either search one of the locations listed in I.PROBLEM for the appropriate files and copy them onto the other location since that may be where your new Bitcomet is looking. I have no idea which BC version uses which directory but it should be fairly simple to just look in both.
But if none of those locations has the xml file, then it may be gone forever and you'll have to do it the hard way (read next)
c) If you can't find the task list xml file, then sadly you'll have to browse the torrent folder and rehash all your unfinished tasks. The torrent folder can be found in the locations presented in I.PROBLEM. All your past removed and active torrent tasks are here... and I mean ALL. Even those you've previously removed from the list, it may be fairly cluttered so just dig up the ones you need, double-click or drag them to the BitComet window and do a hash check for each one. For most people this would be no problem since they only keep a few tasks ready for seeding, but others like me who have almost or more than a terrabyte of files, hash checking is nothing but an unnecessary hassle. So, learn how to prevent the problem by reading on
III. PREVENTION
Before upgrading Bitcomet, export your files first (thanks to royhard for this advice). On Bitcomet select File->Import and Export. Then install the new version, and if you have any problems import the file you just exported. If there was no problem during installation, then you have nothing to worry about and you can keep the exported file as a backup in case you ever need it.
That's it 
, I hope that helped somehow!
Also, it would be convenient if BitComet actually specifies where it keeps the torrent task list in future updates.
