From the kernel.log you have quite a few I/O errors and this can be indicative of a failing HDD. I'd make sure you have everything you need backed up and then test the HDD with an appropriate low level disk utility and "Disk Utility" is not appropriate for the needed low level check.
Jul 31 21:37:51 new-host kernel[0]: disk0s2: I/O error.
Aug 1 06:50:19 new-host kernel[0]: disk0s2: I/O error.
Aug 1 07:21:12 new-host kernel[0]: disk0s2: I/O error.
Aug 1 07:35:21 new-host kernel[0]: disk0s2: I/O error.
...
Aug 1 16:08:04 new-host kernel[0]: disk0s2: I/O error.
Aug 1 16:09:13 new-host kernel[0]: disk0s2: I/O error.
Aug 1 16:10:23 new-host kernel[0]: disk0s2: I/O error.
Aug 1 16:11:05 new-host kernel[0]: disk0s2: I/O error.
Message was edited by: WoodyZ - Removed most of the I/O error messages, didn't realize how many there was as I used grep to extract it from the kernel.log and just copied and pasted it all.