I think your problem is that a normal keyboard will initialize with the PC at boot up. This involves the PC sending different commands to the keyboard, and the keyboard responding to them.

You might want to try plugging in a standard keyboard, boot the PC, and while its still on, unplug the keyboard and plug in your pic and see if it works then.

Heres an example of the 2 way communication that happens as the keyboard inits:

Code:
    Keyboard: AA  Self-test passed                ;Keyboard controller init
    Host:     ED  Set/Reset Status Indicators 
    Keyboard: FA  Acknowledge
    Host:     00  Turn off all LEDs
    Keyboard: FA  Acknowledge
    Host:     F2  Read ID
    Keyboard: FA  Acknowledge
    Keyboard: AB  First byte of ID
    Host:     ED  Set/Reset Status Indicators     ;BIOS init
    Keyboard: FA  Acknowledge
    Host:     02  Turn on Num Lock LED
    Keyboard: FA  Acknowledge
    Host:     F3  Set Typematic Rate/Delay        ;Windows init
    Keyboard: FA  Acknowledge
    Host:     20  500 ms / 30.0 reports/sec
    Keyboard: FA  Acknowledge
    Host:     F4  Enable
    Keyboard: FA  Acknowledge
    Host:     F3  Set Typematic Rate/delay
    Keyboard: FA  Acknowledge
    Host:     00  250 ms / 30.0 reports/sec
    Keyboard: FA  Acknowledge
The above is copied from: http://www.computer-engineering.org/ps2keyboard/