How long dose it take for a collection agency to sue after a threat letter?

Ok i had some money problems like 6 years ago. I opened in june of 2000 a capital one credit card and used 2600 on that. mainly for college stuff. I only made 3 payments and moved to MN. I never recived anything til a year ago 04/06 a letter from a lawyers office demanding 3400 now or else we will sue. Now in august i my boyfriend got a call from a collector demanding 4100 now. the collector told my boyfriend if he fails to give me that message, he will be arrested with possible jail time. Can someone give me some advise on this.