Not sure what the problem is. I just rotated a water texture around the Y-axis(in object space) on a cylinder for 360 degres over 4 seconds (90 degrees per second) and it works fine. 1. At 0 seconds 0 degrees set a keyframe. 2. Moved scrubber to 1 second, entered 90 in the y axis rotation in the edit texture and added keyframe. 3. repeat step 2 until you reach 4 seconds entering 180, 270, 360 respectively. If you want I can send you the file.