AS1804WSMI Troubles

I bought a 1800 a little over a year ago (AS1804WSMI-XPP-DTP4-340-3.2G/256*2/80GB/SUPERMULTI/17"WXGA/802.11G US) and have been having probs every few months with it.
I bought in new in Febuary of last year and had to send it back to Acer in May when it suddenly froze. After attepting to reboot it would just give a blinking curser after POST. Acer sent it back with a note stating that the hard drive had been replaced.
In September, it started trying to run primarily run off the battery. With the high battery consumption of the 1800 series, this presented a major problem. Again I contacted Acer and was sent a replacment power supply. Unfortunaly still same prob and back it went again. This time they replaced the mother board.
Once again in January, I suddenly had a prob with the blinking curser when trying to boot. Again returned to Acer, this time returned with a new mother board and hard drive both. They also upgraded to OS to Media Center Edition. No complaints about that.
Here we are now in April and once again it is back with acer after the dvd-ram drive quit. Glad I got the extended warrenty. Still recognizes the drive but will not recognize any disk in the drive (CD,DVD, etc.) Considered trying to re-install the OS before calling them, but hard to do when can't use the optical drive. Havn't got it back yet to find out end results of the problem this time.

Don't get me wrong, the system has been great when it works. I just rather discuraged by the plague of problems. Has any one else had the kind of issue or know what may be contributing to the failures.