I'm running Java SE Development Kit Update 25 (64-bit).
It appears that I'm unable to run both Eclipse and Minecraft at the same time. This is really really weird, since I can easily start two instances of Minecraft (but not of Eclipse).
I'm guessing that the reason for this bug is that Eclipse is looking for other instances of itself when it starts (because it doesn't want to start more than once).
Is there any way to fix this?