If that doesn't resolve the problem then I would try a new motherboard battery. The loss of hardware configuration settings can be an indicator of the battery failing. A new 3-Volt, CR2032, coin cell battery can be purchased for around $3 (US) and is available at any Radio Shack, computer stores and most discount stores like Wal-Mart. For $3 it is a very cheap item to rule out as the cause of the problem. You can click here <ADMIN NOTE: Broken link has been removed from this post by Dell> for information on how to replace the battery from your model's on-line Service Manual. While the battery is being changed I would recommend clearing the NVRAM by the procedure I have listed below.
With the machine unplugged from the wall remove the battery from the motherboard. Then with the machine still unplugged press the On button for 30 seconds to dissipate any remaining electrical charge on the motherboard. Then re-install the battery, plug the machine back into the wall and see if it will boot normally.
You're very welcome. Glad to hear the old posting helped you out. The answers to many a problem are already in posted in the forums here. Unfortunately not many people take the time to search them out like you did.