Mark,
The USB ports on the Pi are very underpowered. They were only designed to run things like mice and keyboards, which use very little power. Unless you do some fuse mods inside the Pi, the only way to get reliable WIFI is to connect the dongle to a powered USB HUB and then attach this HUB to the Pi. I modified the fuses on one of my Pis, I can run WIFI now powered right from the Pi. However, it will still crash and reboot if I hot plug the WIFI dongle. If you want to hot plug the WIFI dongle, the only way Iknow of is to use a power USB HUB.
With the HDMI, I found that the HDMI cable must be connected at the time the Pi boots and the TV must be turned ON with HDMI selected. If it does not find a valid downstream HDMI device at boot time, it appears to then disable HDMI. I would try again with the TV connected and tuned to HDMI before you power up the PI. Some LCD monitors have a DVI connector on the back. I got a DVI to HDMI cable from Ebay and found that works as well.