Sorting in Word 2000

There must be a reason why I am having this problem. I have a long list of IP Addresses, expressed as numbers, e.g., 68.39.165.56, followed by a colon and a port number. (They are from a very large log table generated by my firewall and I want to investigate some of them). I began with a text file with all the values separated by tabs, each line representing a transaction or activity. I converted it into a Word file. To sort by IP Address I converted that text to a table and the IP Addresses I want to sort are in one of the columns, here column 4. Another column (#5) is my own IP Address, similarly followed by a colon and a port number. Word (Table, sort) sorts column 5 perfectly; since all the IP Addresses there are the same, the sorting is actually by the port number at the end. However, column 4 remains a mess. There seesm to be a little sorting, but it seems pretty random. If a particular IP Address occurs, say 30 times, after the sort there will be groups of that number scattered throughout the "sorted" table. I can't figure out why I can sort this stuff in one column but not another. Any ideas?