Lpc2000

I am using the Keil uVision development environment with the GNU tools
for a Philips LPC2148.  Using the version of GCC currently being
shipped with the debugger (3.3.1 or some such thing - it's 2.5 yrs
old) I stepped through the branch to _start at the end of my startup
assembly file that sets exception vectors, stacks, etc.  It bounced
around a bit then hit a SWI instruction and decided that was
undefined.  I loaded up gcc-4.0.2 and now I am seeing SWI
as the third instruction of _start.  Furthermore, it is SWI 0x00123456
which is really weird.  I checked the linker map to verify that it was
getting the library from the right place, and things looked reasonable
there.  In the Keil tools I am using support for calls between ARM and
THUMB, compiling THUMB code, and enabling ARM/THUMB interworking.  I
did not give the linker any additional include path or commands beyond
what the Keil tool sets up.  I have also tried turning off all the
THUMB stuff to do a straight ARM system, but it didn't help.  Any
suggestions on where to go from here would be greatly appreciated.

Rebekah