I, too, am having problems installing the "universal" installer for Windows. I have had problems with both the x86 and x64 installers. I've noticed that many others here have a similar problem. For this reason, I created a ProcMon.exe log file to help diagnose the problem. I have it available but I am not uploading it now because it is 20+ meg in size and extracts to almost a gig. (Not unusual for ProcMon unfortunately.) Several errors occurred within this log file and should prove helpful...
What I experienced when I tried to install lastpass_x64.exe is that I cannot get past the file installation page. I see a progress bar and then another and then another and they never stop appearing. Further, when I go check the LastPass directory, NO FILES ARE INSTALLED. The previous files are erased but no new files installed.
Big question, is java used in this installation? If it is, I have upgraded to version 7 which is now the default version for Java. This perhaps could be an issue if Java is used.
Last, if someone would like the log file I created, let me know where and how to send it. Regards.
P.S. I can install the individual Firefox 2.0 addon with no problems so I am not completely without Lastpass. However, I cannot get the IE 9 version of the installer to install at all using any of the installers. It hangs up too!