This seems to happen mostly on my main save, which is about 12 mb, but as the title suggests, every 40 to 60 seconds the game freezes for about 5 seconds, and it keeps doing this. I don't think it has done it with other saves, but I did notice some freeze with another one I've played a good bit, just perhaps not as long. I honestly cannot recall if I've had this for a while, but I certainly seem to be noticing it more, and it seemed to have happened after the 1.7 patch. I did some reading and it seems like it's either save bloat, or there is a problem with the 1.7 patch.
Some quick specs;
CPU: Intel Quad 3.0ghz,
GPU: nVidia GTS 450
RAM: 6 gigs
OS: Windows 7 64-bit