That looks like an update maybe, not quite that big when java updates, but close
play a game locally to see if it's the PC, if it is - see above
I'd recommend lowering your cl_maxfps drastically for diagnostic purposes, like to 30 or so. (can set cl_async 1 and keep your r_maxfps high so it should be tolerable except for possibly stymieing your jumps a bit.)Awhile back, there was a period where my ISP started getting spikes like that when I sent a lot of packets/sec out the port. Lowering cl_maxfps worked around the problem. (Lasted a few months, as i recall.)So, might be worth a try...