Any advice I could give would be a blind guess - probably less useful than the responses you've received... but just to let you know your thread is not invisible.
I also have an HP mouse - M/N M-S69. It seems to cause no issues - even though connected through a 4-port KVM. (Monitor is another story.)
On my 12.04 system, there is a /dev/input directory with files mice and mouse0.
Found this in a help file:
Check that the mouse was recognized by your computer
Type Ctrl+Alt+t to open the Terminal.
In the terminal window, type xsetpointer -l | grep Pointer, exactly as it appears here, and press Enter.
A short list of mouse devices will appear. Check that at least one of the items says [XExtensionPointer] next to it, and that one of the [XExtensionPointer] items has the name of the mouse to the left of it.
If there is no entry that has the name of the mouse followed by [XExtensionPointer], then the mouse was not recognized by your computer. If the entry exists, your mouse was recognized by your computer. In this case you should check that the mouse is plugged in and in working condition.