Today I got a failure to log in, saying that my computer needs to be cleaned. Yesterday I switched from the stable version to the development version, so I could use SkypeWeb. This could just be a coincidence, but it could also mean that the development version does something to trigger this and the stable version does not.
This also made me wonder if Miranda IM could be the reason why I get captcha requests when posting totally innocent links, like Wikipedia.
Anyways, I deleted the DeviceID and I can connect again. There was no need to go through some stupid computer cleaning process.