I just built the Minty Boost this morning hoping to take it on a backpacking trip to the Tetons this weekend. It is saying that the device is not supported when I plug in my phone. It does however work when I plug in a co workers iPhone 3Gs. The pins are reading five volts/1.92 volts.
The 1.92v is slightly low for the data lines. You could try swapping out the 75K resistors for something like 68K to boost that up a bit. But you might want to calibrate your meter against a known voltage first to be sure that is an accurate measurement.