Hi,
I am using Template Corporate and installed GK5. In fact, while I could change the design with "stlye" function a bit, the color change by "Suffix" such as redtabs etc did not work at all: No reaction.
After a while and looking to the sample installation (GK ... quickstart) I deleted Tabs GK5 and installed GK4 instead.
Now everything works fine.
Seems GK 5 does have an issue with Corporate Template.
LG
HH