The original post has a quite weak rig listed... However I would refrain from updating much for 2 reasons:
1) This immediate problem is most likely an HTC bug they're fixing, from recent discussions I've seen
2) Any updates to that system would be stop-gap in nature. You can only add so much ram, but the ram is a slower type with limited bus speeds, etc. You can go the budget route of "just to tide me by" upgrades but from my own personal experience this is more costly and aggravating in the long run. You get the lowest upgrade possible every time? Well that means you have to keep doing it constantly. I saved up a year ago and did a full system upgrade and it's still going strong a year later. If I'd kept tacking on an extra bit here or there to my older system it wouldn't be nearly as good as my current one.
A computer relies on the inter-relation of many parts. The RAM relies on the motherboard, which can accomodate different CPU speeds, which need better power supply, which also dictates what video card you can install, etc... It's better to just save up and get a new system all at once if your current one is so dated.
So, outside of the "Wait for it to get fixed" part my ONLY suggestion for immediate upgrade would be: Ditch Vista. It's utter crap. If you get Win 7 (make sure you get x64 bit) you will see improved overall performance, and then when you upgrade can move that installation over to the new system. Win7 isn't cheap (stupid Bill Gates...) but Vista is so rubbish that 2GB ram is the bare minimum for the average install. Idle at the desktop most copies I've seen use 1GB just to do nothing. Even paring that down gets it to the 750MB range. It's crazy.