It is likely a client issue. It may be grabbing additional resources through the process that it is using to perform. It could also be an error in the process. It's been reported and we hope to have a fix soon.
Just to be sure, I tried PvPing for quite a while without restarting my client from earlier. Still no crash multiple hours later despite numerous PvP battles -- but many others in the PvP matches crashed repeatedly, usually saying that they were experiencing symptoms like mini lag spikes, brief periods during which the game would freeze momentarily, etc.