One fix that worked for 0.53 but doesn't seem to be that effective on the alpha is:
uninstall NMM, make sure the program folder is empty, then reinstall it. (seems to be caused by a .dll file unable to update itself on some systems)
If this still doesn't fix it for you then please:
Go in the Control Panel, Programs, Programs and Features, and check the installed program list, please make a screenshot of all the Microsoft .Net elements you got on that list.
Also try going in the Settings menu (gears icon) and disable "Enable mod info side panel" check if his helps with the UI lag (it is not a fix but can help in the meantime).