This is a very odd and uncommon bug. Here's a few things I'd like you to try and test it out in-game after every step:
1: Update your graphic card drivers and direct X
2: Open your setup.exe and change the top bar to something else (try every option. Make sure you change the setup.exe in normal mode and administrator mode, if this doesn't work change it back to what it was and proceed with the next step).
3: Disable UAC settings in Windows completely
4: I think you're using an nvidia graphics card if so: Open your Nvidia control panel, click on Adjust image settings with preview, tick the "Use the advanced 3D image settings. After that click on the "Take me there" behind the option you just ticked. In the menu that you get click on global settings and go down the list to "Texture filtering - Negative LOD bias", set that option to "Allow" and make sure it's not on Clamp.
Changing this setting will apply to all your games etc. So if it's causing issues with anything else you can change it back by clicking the "Let the 3D application decide" option at the "Adjust image settings with preview" menu.
5: Try running the client in compatibility mode for Windows XP SP3
6: If the problem persists try typing /lightmap in the game and see if the bug remains.
7: Install mousefreedom from here: http://ratemyserver.net/index.php?page=download_tool and place it into your RO folder
If after those things the issues persist, let me know. :)