Sounds like you killed the power to the system while it was still booting to Windows. Even though nothing was on your screen, sometimes it won't show anything until it actually gets to the login screen.
If I were you, I'd check that the RAM is still actually clocked at what you set it at in the BIOS. If so, you are probably good. However, I 'd ask, why are you manually setting to 3400mhz and not just using XMP or DOCP to have the motherboard automatically set the proper RAM timings??