Like Jimp said, pfsense can load just a touch slower than other installations. What may have been happening before is the previous installations you used before (linksys/netgear/m0n0 etc…) would boot up before your computer gave up trying to get an IP and assigned itself the 169 address. Once your machine gets that 169 address, it gives up trying to get an IP, thus you have to release/renew.
Maybe you can increase how long your PC tries to get an IP through a registry tweak if this concerns you. Otherwise turn the pfsense box on first, give it a 30 second head start and then turn the PC on. Or leave the pfsense box on 24/7 :-)
@scrotyballbags:
Thanks, this helps, but why does it only do this with PfSense? The router I was using before would be ok when restarted while my PC was on…