This is an issue with the alpha channel of the texture, not [UV coordinates][1]. The alpha channel of an image (if the image has one) contains transparency information for each pixel.
I suspect that the alpha channel of your second texture (the "miss" one) is the same as the alpha channel of the original texture (presumably it wasn't modified when you changed the text). You can edit the alpha channel of a TGA file in Photoshop; [this tutorial][2] explains how to do so.
Briefly, if you open your TARGA file in Photoshop and go to the *Channels* tab, you should see layers labelled *RGB*, *R*, *G*, and *B*, as well as one named *Alpha*. The alpha channel only uses grayscale information: white is fully opaque, black is fully transparent, and shades of gray are translucent. In your case, you'll probably want to select the area containing your text on the *RGB* layer, expand your selection (using *Select* > *Modify* > *Expand...*) to make a border around it, then switch to the alpha layer and fill the selection with white (using *Edit* > *Fill...*). When saving the TARGA, be sure to check the "Alpha Channels" box and select 32 bits/pixel (regular RGB with no transparency is 24; the extra 8 bits encode the transparency data).
There's additional information on the use of alpha channel masks in Photoshop [here][3]; note that they're often used to save selection areas rather than as true alpha channels. Also, you may want to consider using another image format with more straightforward transparency, such as PNG, unless you're using the texture with a reflective material shader (some of which require certain alpha channel information that's easiest to set up using TARGA files).
[1]: http://en.wikipedia.org/wiki/UV_mapping
[2]: http://tutorials.robbiegee.com/ps_tga.htm
[3]: http://helpx.adobe.com/photoshop/using/saving-selections-alpha-channel-masks.html
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