Thanks for the response. I was using the latest version according to "Check for Update" so that wasn't it.
This morning there was an upgrade and it still looks like it has a memory leak. Watching memory usage it's increasing by 2-3MB per second with CPU around 15% constantly. Process Explorer gives a nice graph too.
I've read about potential issues with Windows Defender and other AV software but that's all disabled too.
I'll try checking the disk but haven't had issues with any other applications...