Hello Chan,
ViEmu should have removed the VS keybinding of Ctrl-F the first time it was run. That way, Ctrl-F would be free for interpretation by ViEmu as scroll-down. It is weird that it didn't happen in your case.
ViEmu saves these clashing, removed keybindings for restoring when you deactivate ViEmu (Ctrl-Shift-Alt-V). That way, Ctrl-F regains its meaning when a non-vi(m)er colleague must use your computer.
One simple fix is to just remove the VS keybinding of Ctrl-F, using the VS interface in Tools|Options|Keyboard, and removing the mapping of Edit.Find. The only drawback is that the binding won't be dynamically adjusted when ViEmu is toggled off.
For a better fix, can you go to Tools|Options|ViEmu -> Keyboard, and post here what that dialog shows?
Regards,
- Jon