Sorry to hear about your PX not working anymore.
The Ricoh G700 however could be a good upgrade. In terms of Image quality it is somewhat better, not only than the PX but also the other waterproof compacts which Ricoh have announced since. The problem which Ricoh have with their current waterproof WG-series of compacts is the noise reduction being too high and no option to lower it. At least the issue with oversharpening can be dealt with.
I wrote a short review of the Ricoh G700 with full size sample images for some time ago. http://dpreview.com/forums/thread/3112288
Other than the occasional grey looking noise. Based on the official sample images from the G800 I would definitely go for the older G700 even if the price had been equal. The G800 manage to ruin foliage quite well unlike the G700, with NR and oversharpening way too high. I'm not going to bother review that one simply because the image quality is not good enough to make me interested. I always go for cameras with acceptable image quality when viewed at Full-size. That's also why I so far have ditched the WG-series so far.
The older Ricoh Caplio 500G and 500SE uses even less NR than for the G600 and G700. The downside with the the 500SE however is that it is bulky and also that movie-mode is next to useless as that specific quality is so bad. There is a slight occasional purple cast which sometime can show up in images with the 500G / SE. But by using white balance preset Cloudy/Overcast it is possible to deal with that problem for most of the time easily. G700 have ok hd-video imo but it can't refocus once the recording have begun.
There is one so far inexpensive new in box Ricoh 500SE on EBay with 5 days remaining and the sell have good reputation. http://ebay.co.uk/itm/Ricoh-Caplio-500S ... 4877f6e56f
G700SE with the Gps. http://ebay.com/itm/RICOH-G700SE-12-1-M ... 4d2b5559da
Not a bad price for that one either. These rugged and shockproof Ricohs was expensive as new.
Other good but not new waterproof cameras with good image quality are Pentax Optio W60, Canon Powershot D10 and The newer Powershot D20 is also ok to me when it comes to image quality. I liked the very little NR which was applied but not so much the slow zoom, the UI, shape/grip of the camera or the somewhat stiff shutter-release button.