MikeChat: He did show his /window switches. If you look above at my test, I used the exact same switches without any problem.
WarlockW: Try my test exactly as I typed it before. Use my examples for text to add into the window. Don't use your own. See what results you get.
Also, please paste your entire code that you are using. Include your code for making the window, adding lines to it, and trying to use $fline on it. Make sure you let us know what the lines you are adding are and what your %text-to-find variable is set to. If it is not working, it's some error in your code or else some other script causing a conflict.