I did a little digging for you, and it looks to me like you have not allocated enough memory on your PS for your site to run. It can be tricky to get the right amount of resources allocated, as it can depend to a degree on the number of connections being requested, and your site looks pretty popular and has a lot of googlebot activity pounding it.
The result of running out of allocated memory, is that 500 internal server error you are seeing. You can see what is happening by checking your memory usage using free:
free -m
total used free shared buffers cached
Mem: 150 140 9 0 0 0
-/+ buffers/cache: 140 9
Swap: 150 0 150
(that's about 9 mb free)
and even see it happening if you try to inspect your access logs:
tail -10000 access.log| awk '{print $1}' | sort | uniq -c |sort -n
-bash: fork: Cannot allocate memory
I see that the initial problem you reported here (your broken links) was fixed by support and the fix reported to you at 06:43 yesterday morning.
This newest issue is another thing altogether, and it isn't something that we can fix for you. This is your responsibility to manage, not that of suppoprt.
To fix this you have a couple of choices (and they are yours, not ours, to make):
1) Decrease the amount of memory required to display your site
2) Increase the amount of memory available to your site.
One takes works and expertise, the other takes money; representing here that your initial problem remains unfixed when it was fixed almost 20 hours ago, and intimating your current issue is due to a DreamHost failing, won't help in any case.
I have asked a tech to respond more fully to your ticket about the 500 errors - but I'll bet you he tells you essentially the same thing.
--rlparker
--DreamHost Tech Support