high-pitched tone from pc speaker

[Michael Haro]

I recently installed FreeBSD 4.8 on a server at work.  I cvsup'd and
installed an updated world and installed a few ports.  I also
rebuilt the kernel to support dual processors.  I don't know if this
always happened, but now the on-board pc speaker (the one that goes
beep, not from a sound card) emits a high-pitched tone a minute or two
after boot.

I wasn't able to find anything in google relating to this problem.
Has anyone else experienced this problem?

I'm not really sure where to look to try to remedy this issue.

Thanks,

Michael