At least 2-4 times a day, unless I'm in a bad mood. My nastiest wrecks are at night, when I don't realize there's a hill right in front of me.

I misjudge a lot of bridges, too,

AMD Athlon X2 4200+ dual-core- 2.2ghz per core
MSI GeForce 9400 GT- 550mhz core, 512mb VRAM
2gb DDR RAM, dual 17" monitors (one Acer panel, one KDS boat anchor)