I can edit with ease and stability footage shot in PH1080/30p but PH720/30p clips will not even move to the Timeline without crashing the program. I use Panasonic's HMC150 SDHC card camera on a Sony Vaio laptop, AW220J with 4GB of RAM.
Recording video at PH720/30p is recommended for the best quality HD Television reproduction and for DVD mastering, so it is frustrating to be denied this option due to PE 7's inability to process the information.
This is an AVCHD program. Check to see if this camcorder is shooting in 5.1 audio or stereo. The chief reason for the problems you're describing is users not having their Premiere Elements project set up to match the video.
When you start a new project, ensure that it is set up as an AVCHD project, as importantly, make sure that, if your video was shot in 5.1 audio, you choose an AVCHD 5.1 audio set-up!
If you don't do this, your video will not load to video track 1 and you will not be able to use timeline mode to edit!
AVCHD is also a very intensive format to edit, so it's very important that you have your computer completely up to date. This includes ensuring that you have the latest version of Quicktime, RealTek drivers, firmware for your graphics card and every Windows update. Many of these updates don't load automatically, so you may need to go to the manufacturer's sites to ensure you have the latest.
Particularly when editing on a VAIO (notorious for Sony's tweaking of the operating system), you want to ensure that every function of your computer is operating at their optimal, particularly when doing intensive work like this.