Lpc2000

I'm trying to get I2c up and running on my 2106 board and am seeing 
strange things. Basically, when the LPC2106 brings SCL low I see the 
line dropping only to 1.5V rather than 0. I can verify this by 
switching P0.2 to GPIO mode and outputting 0.

SDA fluctuates between 0 and 3.3V as I would expect.

I do have another I2C master on the bus - a TI TUSB3410. When it drives 
I2C SCL fluctuates between 0 and 3.3V. The TI chip is in suspend mode 
at this point, as far as I know it shouldn't be impacting the I2C bus.

I have 10k pullups on SCL and SDA.

Does anyone have any ideas as to what might be causing this or where I 
can next look?

Thanks!

Shannon