Ok ... A little more detail here:
I moved to 2.0.33, and build a kernel with SMP support, removing the -fomit_frame_pointer flag and added -g.
My server crashed this morning with the same error message, the address being somewhat different, but close enough to the original that I suspect the address to be the same function, in relation to 2.0.32
The scheduler was re-entered (apparently) from __wait_on_buffer in /usr/src/linux/fs/buffer.c, line 121.
I also read elswhere that enhanced RTC support is needed for the kernel, which had not been added before.
Could this be a cause of the crashes?