Lpc2000

I'm having difficulty with getting the I2C to work (with the LPC2214 as 
the master). I can get as far a valid start condition (0x08) and 
generate an interrupt, but I can't get the clock line (SCL) to 
oscillate. If I debug, it appears that both the clock (SCL) and the 
data line (SDA) go low simultaneously after start flag is set (STA in 
the I2CONSET register).
After the interrupt is generated, I attempt to send an address, (by 
setting the contents of the I2DAT to a valid PCF8574 slave address 7-
bit value + a "0" for a "write" (ex. "0x40")). Both the SCL and SDA 
lines appear to remain low until the start flag &/OR the Interrupt flag 
is cleared (by setting either the STAC &/OR the SIC bits in the 
I2CONCLR register). I've also tried to set the address value in the 
I2DAT register after clearing the start &/OR interrupt flags with the 
same result.

Note: I do have 10K ohm pull-up resistors (to 5v) on both the SDA and 
SCL lines.