Booting problems - USB/firewire related?

Core 2 Duo E6600, Asus P5N32-E SLI.

I removed my cpus heatsink/fan today and cleaned both surfaces and applied some new thermal paste. I then reinstalled the heatsink/fan upon the surface of the cpu and locked it onto the motherboard.

I then proceeded to rearange all my cables and clean out the dust ect from my system. After plugging everything back in my system has power but I don't get a singal to my monitor. I have pushed my video card back in and checked it has power from the PSU various times but it hasn't helped. My Antec case does not have a PC speaker so I am not getting any audible beeping feedback.

I noticed later that I had my firewire header plugged into one of my usb connectons upon the motherboard upon my intial boot. Asus warns in the manual that this can damage your motherboard. You can see where I am going now so I will say that on that initial boot the system powered up without smoke or resetting or shutting itself down. However I am still concerned I have damaged my mother board by doing this and this is stopping me from booting my computer sucessfully.

I had no firewire devices plugged in at the time nor any usb devices related to that connection which is for USB add-on plates or front panel.

I have cleared the CMOS to no avail. I have also unplugged everything such as SATA devices.

Do you think my mis plugging could be responsible for damaging something on my board? Ideas?

Thank you for your assitance.