If there's a pattern to the activity surges, could you please identify those windows of time? You say "Japanese evening hours." What does that mean in Japan's time zone? 5pm to 12am? 9pm to 1am? Seems like a subjective description. Something slightly more objective would be helpful, but only if you have that information in the first place. If the surges are random and range from as early as 1pm Japan time to as late as 4am Japan time, then never mind.
For those who want to look up time zones, check out this helpful map:
http://upload.wikimedia.org/wikipedia/commons/e/e7/Timezones2008.png
For fellow Americans, given what red has said, then ideal times to visit Akiba would probably fall somewhere around the following times of day:
Mon-Fri 3am to 11am Japan time
Sun-Thur 1pm to 9pm EST
Sun-Thur 12pm to 8pm CST
Sun-Thur 11am to 7pm RMT [?]
Sun-Thur 10am to 6pm PST
In other words, for most Americans, the best opportunities to load the site would be:
(1) shortly before or shortly after dinner, and
(2) only on Sundays, Mondays, Tuesdays, Wednesdays, or Thursdays.
Equipped with that knowledge, it might be worth trying out for those of you who are having problems. This way, you can help yourselves figure out and you can also help chompy and the staff figure out how much of your problem is because of buggy forum software and how much of your problem is because of server overload during peak usage hours.
For those of you who can only access Akiba-Online on the weekends, my suggestion would be
aim for Sundays because your Sunday is very likely going to be Japan's workweek Monday.