TMS320F28027: Cannot use I2C and SPI buses together but both work fine when used separately

Part Number: TMS320F28027

I'm trying to use the I2C and SPI buses on my project.

The problem is that when I attempt to use both together by uncommenting each respective block of code, the SPI and I2C don't work right.

Both blocks work perfectly when the other is commented out.  I use the SPI bus to program a DAC and PGA, and use the I2C bus to program a bank of LEDs.

I'll paste the relevant code below.  As an example the code labeled "ERROR: HANGS HERE" gets stuck waiting for an ACK when the SPI block is also compiled in but always works when the SPI code is commented out.

I realize it's difficult to make suggestions based on code snippets, but does anyone have an idea where I should look for the problem?  This program is running from flash and I copy time-critical functions to RAM.

// Using the I2C bus.  Works fine if SPI is not compiled in.

void set_leds(Uint16 slave_addr, Uint16 on_off)
{
    int i;
    I2caRegs.I2CSAR = slave_addr;
    I2caRegs.I2CMDR.all = 0x4620;       // FREE, MST, TRX, IRS
    I2caRegs.I2CCNT = LEN_ON_MSG;
    I2caRegs.I2CMDR.bit.STT = 1;        // Start condition
    I2caRegs.I2CMDR.bit.STP = 1;        // Stop condition will be generated when CNT=0
    if (on_off == ON)
    {
        for (i=0; i<LEN_ON_MSG; i++)
        {
            I2caRegs.I2CDXR = on_msg[i];
            while (I2caRegs.I2CSTR.bit.XRDY == 0);  // ERROR:  HANGS HERE
        }
    }
    else
    {
        for (i=0; i<LEN_ON_MSG; i++)
        {
            I2caRegs.I2CDXR = off_msg[i];
            while (I2caRegs.I2CSTR.bit.XRDY == 0);
        }
    }
}
...
...
...
// I2C initialization.

void i2c_init(void)
{
    I2caRegs.I2CMDR.all = 0;                // Disable I2C module and clear all options
    I2caRegs.I2CFFTX.all = 0;
    I2caRegs.I2CFFRX.all = 0;

    // Set the clock rates:
    //    Module clock rate: (CPU clock)/(IPSC + 1) = 10 MHz.
    //    I2C bus clock divider registers: 10 MHz/((ICCL+d)+(ICCH+d))
    //      where'd'=5 (see sprufz9d.pdf) produces bus clock at 300 KHz, 50% duty cycle.
    I2caRegs.I2CPSC.all = 5;                // 60 MHz/(IPSC+1) = 10 MHz
    I2caRegs.I2CCLKL = 3;                   // ICCL+d = 6
    I2caRegs.I2CCLKH = 3;                   // ICCH+d = 6
    CLK_enableI2cClock(myClk);
    I2caRegs.I2CSAR = TLC59116_SLAVE_ADDR_60;
    I2caRegs.I2CMDR.bit.IRS = 1;            // Enable I2C module
    while (I2caRegs.I2CMDR.bit.STP != 0);
    return;
}
...
...
...
// SPI initialization. Works fine if I2C is not compiled in.

void spi_init()
{
    CLK_enableSpiaClock(myClk);
    SPI_resetChannels(mySpi);
    SPI_setCharLength(mySpi, SPI_CharLength_16_Bits);
    SPI_setMode(mySpi, SPI_Mode_Master);
    SPI_setBaudRate(mySpi, SPI_BaudRate_500_KBaud);
    SPI_setPriority(mySpi, SPI_Priority_FreeRun);
    SPI_enableChannels(mySpi);
    SPI_disableLoopBack(mySpi);
    SPI_enableTx(mySpi);
    SPI_setTriWire(mySpi, SPI_TriWire_ThreeWire);
    SPI_setClkPhase(mySpi, SPI_ClkPhase_Delayed);
    SPI_setClkPolarity(mySpi, SPI_ClkPolarity_OutputRisingEdge_InputFallingEdge);
    SPI_enable(mySpi);
    return;
}

void spi_fifo_init(void)
{
    SPI_enableFifoEnh(mySpi);
    SPI_resetTxFifo(mySpi);
    SPI_clearTxFifoInt(mySpi);
    return;
}