Two things...
My Sony DSC-T1 stopped working after an OSX upgrade. I found that there was a Sony firmware upgrade for the camera which cured it.
Secondly, open the application Image Capture. This is the program that actually detects the camera is connected and then opens iPhoto. Check that the camera option is correct in the Image Capture preferences.
Finally, if desperate, you can get a card reader and remove the Memory Stick from the camera and put it in the card reader. Mine would then load as normal and open iPhoto.