Sounds like you fuse rating maybe a little low. What wattage are you running? Your system might be pulling over 60 Ampies, therfore it would blow your fuse.
The fuse up front is intended to protect from your power wire grounding to the car chassis on its run to trunk. I use a 150 Amp fuses, because if it does short to chassis it will blow almost any size fuse before it starts a fire.
Another cause could be an amplifier shorting in its power supply, thus causing it to suck enough juice from the battery to pop thy fuse.
Make sure you have additional fuses close to the amps to protect them from damage.