Probl’y could if we knew what OS you were using. That’s one of those things mentioned as important to include, in that topic titled, “PLEASE READ BEFORE POSTING”, which you should have read before posting.
Go into BitComet–>Options and make sure that BC is set as the default handler of Magnet Links.
Possibly you’ll need to also go into the Options page of your DC++ client and make sure it’s not set as the default handler of Magnet Links, so it doesn’t hijack your association again.