stuck when splitting nibbles in C

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C

Hey guys, I was wondering if somebody could spot my mistake(s)...

All i'm trying to do is send a byte over a 4 bit data line in C(also with an enable line). Its quite fustrating because If I send EITHER the upper or lower nibble (with a longer delay and some LEDs) the data of both nibbles comes out as planned. Its when I try to send them consecutively in a switch statement things seem to go a bit pear shaped...and heres the code...

case 0x02:                         //case 0x02 from firmware
        IDENT_PORT = 0X00;
        j = 0x16;                  // bit mask ie, & with 1111 0000 to clear bottom nibble
        upper_nibble = j & 0x0f0;  // 0001 0110
        PORTB = upper_nibble;      // present upper nibble on port b
        RB1 = 1;                   // pulse enable line
        DelayUs(100);
        RB1 = 0;
        DelayUs(100);
        k = (j << 4) | (j >> 4);   // swap upper and lower nibbles of 0x16
        lower_nibble = k & 0x0f0;  // again bit mask to leave the lower nibble (0110)
        PORTB = lower_nibble;      // put on port
        RB1 = 1;
        DelayUs(100);              // pulse enable line
        RB1 = 0;
        DelayUs(100);
        PORTB = 0x00;              // clear port
        break;

If I can provide any other info PLEASE let me know.

Any suggestions would be appriciated, as I'm about to start banging my head against a wall!

Thanks
M.