System Mechanic can remove LastPass from Internet Explorer even after you reinstall it.  To ensure this doesn't happen, make an exception in System Mechanic for LastPass.  Please follow these instructions:

Open SMP 10 by double-clicking the desktop icon
Click the Safetynet link in the upper-right corner of the titlebar (next to the options link)
Click the Re-enable Startup Settings tab
Click on the name of the process in the retrieved list of disabled startup processes
Under the Tasks group (lower left-hand column), click the Re-enable startup link
Click Yes in the Confirm dialog box to confirm that you want to re-enable this process
Click Yes in the next Confirm dialog to confirm that you want to exclude the process from being automatically disabled during subsequent optimizations.