Internal server errors when trying to save a post or comment

Mostly my blog works ok, but every now and then, when I try to save a post, I get an Internal Server Error 500 message and can’t save it. When this happens, I usually go through the text I want to post paragraph by paragraph, saving a little at a time, and the system will save the post bit by bit until I hit a URL, at which point I get the Internal Server Error message again. I’ve learnt now to feed the URL into tinyurl.com, get a replacement, and the blog will accept that. I can’t see any rhyme or reason to WHICH url mess up my blog, other than that they’re mostly quite long, but other times longer urls work fine. There are no special characters in the URLs that crash it.

I’ve also had readers say that sometimes they get the internal server error when posting comments (though I get plenty of comments so obviously it also often works), and other readers say they “can’t get to the blog”.

When other people link to a specific post in my blog, sometimes (and no, not always) simply following the link causes an internal server error rather than getting to the blog post in question. However, if I reload that url (just click the url field and press return) the blog post always appears.

This is incredibly frustrating and since it’s not consistent it’s hard to figure out what the problem is. My server administrators blame wordpress, but I haven’t seen any other complaints about such problems so wonder whether they changed a setting or something a few months back when all this started.

Does anyone have any ideas – could it be WordPress’s fault? Or is there some setting on the server or in mysql centrally that could produce this kind of problem?

I’d *REALLY* appreciate any advice!