Gael Holmes, Software Development team blogged about the T400 & the beep beep beep error. Check out her post and the additional tips from Frank on reseting back to factory..
Comment from Gael's blog -
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Hi Gael,
I had the same "Morse Code" problem on a T400 and thought it was a one-of-a-kind.. 
But, I have some good news for you... there is a Lenovo BIOS update that addresses this and it worked me...
http://www-307.ibm.com/pc/support/site.wss/document.do?lndocid=MIGR-70350
As to the question of how to get the ME back to factory default, here isn the process I use:
In BIOS, select Config-> Intel (R) AMT-> Intel (R) AMT Control- Disable ... exit BIOS and reboot
Then repeat the above enabling the AMT control, and you will be back at factory default- PWD is "admin" again
Frank