HTML Error when uploading photos

Hi, I’ve had several WordPress sites running for a while and suddenly when I try to upload photos I’m getting HTML errors and the file won’t upload. This doesn’t happen all the time, so sometimes the photos upload fine and sometimes they don’t. I used to get the occasional one, but now it happens more than it doesn’t.

It doesn’t relate to computers used, or to the types of photos (I only upload images sized for the web at 72 dpi), or to where they’re being uploaded from, or the speed of the internet (my daughter has the same problem when uploading from her mac on highspeed internet as I do on slow internet on a PC.) I can try a photo several times and it won’t load, then a couple of minutes later it might – if I refresh the page first.

I’ve read other threads on this and the answers are all too technical for me. Also different things seem to work for different people. Also so far, this is an intermittent thing. It just seems to be getting worse.

The site that is causing the most problem for me is but my other sites, http://velvetwingsdesign.com and http://tahlianewland.com are also having the same problem. I don’t know if it’s also happening on my other site http://awesomeindies.net because I don’t post things there.