Here's the way to save texture in correct format in Photoshop.
I use CS3 version and don't know how it works in other versions or not.
1. Select from main menu "File - Save As";
2. Select format "Targa";
3. In Targa options window select "24 bits/pixel" and leave "Compress" option unchecked;
4. Press "Ok".
Then upload texture as usual