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(Use Activity Monitor to check yourself if this is running on clean boot and it likely won't be running, or if you already opened the preference pane as per suggestion, kill MicrosoftMouseHelper process and see the mouse behaviour change). This, I believe, is the issue as it must be run to activate the hardware and software features for the mouse. After trying to learn AppleScript for 2 hours to hack around the issue and adjust my sensitivity settings through an automated script to adjust the preference pane, I remembered there should be a process called 'MicrosoftMouseHelper' loaded for the Intellipoint to work, and I noticed it wasn't running on a clean reboot. The issue for me was tracking speed (and mouse acceleration!) reverting to the OS X default and not using Intellipoint settings.
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I believe I have discovered the real reason why this happens and the cleanest work around (version 8.2 doesn't fix this for me).
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