since you seem to be new to all of this, i provide a few pointers:
it all happened around April 10:
there was the virus, apparently, that we both caught - the scam victim and i, and who knows how many more;
probably we visited same sites searching for free btc lotteries or something like that...
it contained a trojan keylogger that stole information from our computers and sent it to the thief;
my problem was that i had disabled kaspersky antivirus at that time period because i was playing videogames and antivirus lagged my game a lot;
since i had abandoned this account "timeout" soon after ~ April 4,
the thief used the account data to log into this account in my absence and perpetrate his scam;
you can read more about what was the virus on scam victim's reddit post:
http://www.reddit.com/r/Bitcoin/comments/22pbfc/psa_collectcoinsnet_scam_all_btc_stolen_from/the clue to stay safe:
never download unknown/suspicious installers from suspicious websites or where they promise to give you a lot of something for nothing
also, secure your web-browser against attempts to auto-launch suspicious applications, etc.
and the most importantly: use the best tools and employ every level of security available when keeping your electronic money!
