I'm guessing that:
1. IF the reason for the network issues is DDOS attacks
2. They haven't spent the big money it takes to get the hardware + software to prevent DDOS attacks
3. They are possibly using a cheaper solution to the DOS attacks.
4. The 'cheaper' solution is one which will make errors and block some IPs in error.
5. They aren't going to be up front about this and explain it. It's more fun to have customers frustrated and complaining.
6. Just a theory, maybe it isn't DOS attacks.