It is the first thing you need to fix the issue as stated above. For that, you need to run the virtual machine showing the error and go to the Devices > Install Guest ...
If headphones are not working with the virtual machine, follow these instructions, i.e., enable enhanced session mode, install guest additions, etc.
Does anyone know offhand how to remove the guest additions for VirtualBox 3.1 in Ubuntu 9.10? These are the additions that provide mouse integration and X drivers for automatic window resizing.
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