Nearly every time we see one of these that more than a couple people are experiencing, it's because somebody else on the server is using up a good chunk of the resources. It used to be the webserver itself that was the issue - one of our fellow tenants would suddenly use a ton of CPU time and we'd slow to a crawl. Lately it's been the database server getting sluggish. While I can't see what they're doing, I can tell that queries aren't running in normal time and therefore, the box must be busy.
It comes and goes as load goes up and down - it's just one of the things that you live with for the incredibly cheap price of webhosting on a shared server. Unless it's sustained for hours on end, just be patient and try again in a couple minutes. You're probably just seeing a transient slowdown caused by somebody else being busy.