@voder vocoder said:

Read about the Position Texture tool in the User's Guide.

~Voder

Here:
http://download.sketchup.com/sketchuphelp/gsu6_win/Content/D-Modification_Tools/ModTool-PositionTexture.htm

right click the face (with the material in the wrong direction) go to Texture > Position Right click again and go to > Rotate... > choose the angle (I gues 90 degrees)
Note that positioning a texture can only be performed on a single face; not on curved surfaces nor on groups/components (unless you turn on hidden geometry with surfaces or edit the groups/components).

p.s. I merged your two posts (the one in the CMS forum with this one) about the same issue.