Difficulty logging on between 7:30pm EST-9:00pm daily

[Isthisme?]

I just came back to P99 after about a two-year hiatus, and all was going well for the first week or so. Then, suddenly, I couldn't log on nearly at all between 7:30-9pm pretty much every night. It's only this game, and I don't appear to be having any Internet issues. Either I get a connection error or the whole client defaults to 'not responding'. Has anyone had similar or can offer advice?