Can´t open Minecart with Chest (342)

need more than just "HALP! BORKEN!"

to quote many people over time: "Logs or it didn't happen"

Even with such little information, it doesn't seem like an IC2 problem -- I don't believe IC2 does anything at all to minecarts.

Sounds like a Forge bug. Would you happen to have railcraft too? If so, then please ask on the respective forums.