Process Of Designing A Computer Control Program To Control A HF Communications Receiver?

I am in the process of designing a computer control program to control a HF communications receiver (radio), and have found a problem with the Serial port. I am using VB Express Edition 2008. This module of the program is supposed to take an input string from another part of the program, format it, break it into 4 bytes, and send it to the radio in hex form via COM port 1. The problem comes in when you try to enter a frequency with an 8 or a 9 in it. The 8 or 9 is usually replaced by 45, ex.-input 9900, receiver tune 4545. The exact same thing happens with 8's, input 8800 and receiver tune 4545. All other numbers other than 8 or 9 work fine. The strange part of it is that sometimes the 8's and 9's work, and work correctly. For instance, 900, 1900, 2900, 3900, 4900, 5900, 6900, and 7900 all work correctly. This led me to believe that is may only be when the 8 or 9 is in the first position, but that is not the case, it also shows up in other positions as well. All other frequencies that do not have 8 or 9 in them also work. I ran into this same problem with VB Express 2005, and worked on it for weeks before giving up and going back to VB6.0. This same module (with exception of the port open command) runs flawlessly under VB6. I have even tried importing the MSCOMM control from VB6, but it gives the same results. In de-bugging mode, all of the inputs, decimal and hex seem to be correct, so the problem must come in after you click the command button, but before it leaves the COM port.

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