I have the same issue and I'm a premium user.
The site loads OK, but when searching the browser hangs. In Chrome, you get the Wait or Close Page Dialog box and Firefox sends you here: https://support.mozilla.org/en-US/kb/warning-unresponsive-script#w_other-causes
Same in Edge, no browser works, I have to disable Last Pass in order to continue which isn't ideal as I hate having to turn things off and on again.
Windows 10 Pro Build 1803 (17134.472), 64GB Ram, Chrome/Firefox Edge all latest versions. Last Pass version:
Built: Thu Dec 13 2018 16:40:26 GMT-0500 (Eastern Standard Time)
Binary Component: true (Native Messaging version 4.1.48, built Oct 3 2017 16:43:26)
Please let me know if you need further info.