Hello IceWarm,
Firstly there is some really bad advice being handed out here, people who have not got a clue what they are talking about giving you legal advice which could bite you and others on the arse.
You cannot register a domain with a trademarked term and think it is ok just because it is not registered. If you register something like CallOfDutyForum.com the company may know of its existence and permit it to be run because it benefits them, however you will always have the potential threat of them taking the site off you. All websites with TMs registered after the fact used in the same industry are bad faith, all websites that were registered before the TM but pass themselves off are bad faith, so for example you may own Iphone.net registered since 2000 but the minute the you start using the domain to promote your Iphone unboxing videos youre finished. You do not even have to use the domain, if the domain is parked and the links are that of the TM or the TMs competitor youre in the s***. If you own apple.net and use it to sell apples youre fine but I guess that is not what you were doing.
Although in your instance it is too late, for anyone else I would recommend that if you do suspect you are being conned out of your domain you simply send an email to the person who has written to you requesting an electronic copy of the letter sent because it was "badly damaged in the post by water" etc. Be vague "I received a letter from you today can you send this electronically" so that you do not end up tipping off someone who wasnt aware of your existence if it is a scam. If it is a scam then the person would not have a firstname.secondname at gamingcompany or firstname.lastname at lawfirm email address.
The last thing to say is this, although this is blackhatworld building a website on a TM is short term thinking, a poor mans quick buck.