SOLVED:
I decided to leave
Linx running to test for stability. After about 45 minutes, it failed. I tested again to be sure and about 40 minutes in it failed again.
I replaced the CPU with a Pentium D I had laying around and left Linx running overnight with no errors.
However, it looks like I'll have to take a look at the heatsink and check the temperature as the CPU fan is spinning much faster than before.
All in all, replacing the PSU solved the corrupt downloads, and replacing the CPU resolved the stability issues. I'm guessing that the PSU could have damaged the CPU in some way. Perhaps this machine was affected by the lightening storm we had a couple weeks back, but I haven't seen any other computers affected by it.