Hi! I have been enjoying Old world blues on my under powered laptop recently and so I decided to move my saves over to my more appropriate computer.

FalloutNV steam version
Intel duo, quad core 2.66
Nvidia GeForce GTX 275
Mobo P5K/EPU
4gb ram
Windows 7 64bit
dual monitors

And the only mod I have installed is Darnified UI for NV

So above is what I think is all the relevant specs and it's easy to tell my computer should be able to handle FalloutNV with no problems, and normally it does.
I recently installed Lonesome road too, so i'm not sure if that changed anything major to the rest of the game, playing through Old World Blues before I go chasing Ulysses.

So the meat of the problem, after loading up the save I was playing on my laptop I ran into some Robo Scorpions and every single time they fired their tail lazer the game would freeze up for roughly a second.
Fortunately I play an unarmed character so closing in on them forced them to stop using their lazer. Ever since then I have noticed that most energy weapons cause this spike /just/ at the moment of being fired.
Seems to happen with most energy weapons, however not the LAER and not a plasma pistol, I don't have access to standard lazer(red beam) weapons to check, but it does happen with pulse grenades and plasma grenades.
so the list so far is, Sonic Emitter, Scorpion tail lazer, pulse grenades (and mines) and plasma grenades (and mines). The main concern is obvious Scorpions as there are many in the forbidden zone.

Could it be a sound problem rather than a graphical one? the hunch being that after the initial stutter the beams and graphics seem to handle fine and the during the spike the sound fritzs out, I also noticed that even with music turned off,
Old World Blues music seems to continuously play no matter where you are.

Things I have done to try and fix the issue.
check graphics drivers are up to date.
reinstall FNV
set graphics settings low
check mobo is up to date.

TL/DR some energy based weapons cause massive lag spikes just as the weapon fires.