Sometimes strange things happen.
But, they generally don't last for long.
Yes, they are annoying when they happen!
There are three major potential sources for problems:
1) Your Internet Service Provider (ISP) may be having technical problems, overloaded, or working on their servers.
2) The server where DC resides may be having problems, overloaded, or being upgraded.
3) The software on DC might be going through an upgrade. When this happens strange things can occur ... really strange things. But, Andy R. is really good about keeping maintenance "downtime" to a minimum.