I've come into contact with two 2400c, and the only way that made them 100% reliable was to replace a few SMT fuses on the motherboard. If you check the 2400c mailing list it will tell you where, how and why to test them.

Thankfully the 2400c I kept is rock solid. I just scored on eBay a replacment LCD panel for $1, quite a score - my current screen has a large scratch on it.

JB