There is very probably no problem with the fuse - the fuse blows to prevent the wiring becoming too hot and catching fire.
A 15A fuse can handle 180 Watts - it would be good (for you) to know the total wattage of the various lamps being supplied when the fuse blows.
My guess is that there's a short in the wiring circuit causing excessive current - if it's permanently there it will be easier to find - if it's intermittent then more difficult.
Peccavi, April 2010
