How much space do ye 'ave on y'er computer? If ye got a lot of games and whatnot, it may be hampering y'er gameplay with FH. Maps take up a lot of space if they're well done in details. Map packs can get up there in the MB. If ye see that y'er low on space, try getting rid of a few games that y'er no longer interested in.
If y'er good on space, check y'er computer's age. If y'er 'pooter is up there in years, it may not be able to handle the extra files.
I'll keep brainstorming on what may be causing this.