After commuters on the L and B/D (as well as N/Q/R/W) lines had to deal with breakdowns and commuting delays last night, this evening's commute brings delays on the F, D, G and N lines. Apparently a signal problem at 4th Avenue-9th Street Station in Brooklyn is causing the F to be shut between West 4th Street-Washington Square Station and the Church Avenue Station in both directions. The F then runs on the D......