Inspiron 530s startup problems with weird beep and blink codes

I have a 530s that's about  a year and a half old, haven't had any problems like this until today.  I rebooted the system this morning and since then it's been doing the following sequence:

I power on the computer, and then:

--power light is very briefly amber, then turns blue, then very briefly amber again, computer turns off by itself

--computer turns back on by itself, power light very briefly amber, power light then turns blue, then very briefly amber, system again turns off by itself

--computer turns back on by itself, very brief amber power light, power light turns blue, there's a single short beep, system stays on but doesn't boot, fan spins down to normal speed

Nothing is ever displayed on the monitor during that whole process.  The sequence above is absolutely consistent, I've cycled through it five times now and it's been identical every time.  I've checked the various trouble codes at http://support.dell.com/support/edocs/systems/insp530s/en/OM/HTML/trouble.htm#wp1043338, and none of them match up with what's happening.

Any ideas?