I'm a little unclear on which box you unchecked for the mouse, as it shouldn't have needed doing.
He may be talking about the "absolute pointing device", but I'm not sure, either. I've always had problems if that one is checked. Depending on the OS settings selected in VirtualBox, that option is sometimes checked by default.

@hedgeclippers,
Need to know some information about your system's memory. Please open a terminal and enter the command
free and post the output.
To determine the amount of video RAM you have, you'll need to enter a couple of commands. The second command will depend on the output provided by the first command. First, enter:
lspci | grep VGAYou will see something similar to this:
02:07.0 VGA compatible controller: nVidia Corporation NV34 [GeForce FX 5200] (rev a1)
Use the device number shown for your video controller for the second command. On my computer, the video device number is
02:07.0. So, I would enter:
lspci -vs 02:07.0And I would get the following results:
02:07.0 VGA compatible controller: nVidia Corporation NV34 [GeForce FX 5200] (rev a1) (prog-if 00 [VGA controller])
Subsystem: Device 196e:01ad
Flags: bus master, 66MHz, medium devsel, latency 248, IRQ 22
Memory at fd000000 (32-bit, non-prefetchable) [size=16M]
Memory at d0000000 (32-bit, prefetchable) [
size=256M]
[virtual] Expansion ROM at febe0000 [disabled] [size=128K]
Capabilities: <access denied>
Kernel driver in use: nvidia
Kernel modules: nouveau, nvidia173, nvidia-current, nvidiafb
So, the amount of RAM my video card has is 256MB.
In addition, please post the amount of RAM you are using
in VirtualBox for system memory and video memory.