MSP430F5529: MSP430F5529 I2C

Are you stepping through your code?
Just as far as I remember, it goes like this with your code:

1) You send a start with address, and immediately TXIFG = 1

2) You put first char in the buffer, TXIFG = 0

3) You enter some kind of a delay

4) When the address is transmitted and ACK received, MSP I2C immediately starts transmitting the first character you've entered and TXIFG = 1 again

5) The MSP I2C will stall the line after the seventh bit, and will not send an eighth bit before you put another character into the buffer

So if you're too slow (because of the long delay or because of stepping through) the slave might reject the transaction. I don't see the need for the delays, the flag polling mechanism assures that everything is done in time. I also recommend you to check the NACK flag, so use something like this:

while((UCB0IFG & UCTXIFG) == 0)
{
    // Check for NACK while waiting
    if(UCB0IFG & UCNACKIFG) == 1)
        return TRANSACTION_FAILED_FLAG;
}