What is LSASS.exe?

I found this info at the following address, you can check it out, but I don't know if MS has a fix for it yet or if this is the cause of your problem.

http://www.net-security.org/text/bugs/996939945%2C40343%2C.shtml

A damaging local DoS in WinNT SP6a
Posted on 11.8.2001
After attempting to repair the computer with the WindowsNT cd-rom the machine would allow logins, however the machine ran EXTREMELY slow. All available CPU ticks were being consumed by "SERVICES.EXE" and "lsass.exe".

NOTE: ***If testing this vulnerability it is highly recommended that you backup all your data or test on an unused machine. In all my tests after running NT4ALL the computer will be virtually useless!***

This vulnerability has the potential to be very harmful, because NT4ALL can run quite invisibly, and if the payload is attached to a self-replicating email (like many macro virus's), it could render a mass of workstations useless.

Here are links to download NT4ALL from Packet Storm Security:
Newer version of NT4ALL:
http://packetstormsecurity.org/NT/hack/nt4all-101.zip

Original version of NT4ALL:
http://packetstormsecurity.org/NT/hack/nt4all.zip

(All tests were done with the original version of NT4ALL)

3. Exploit

Run NT4ALL once (should put the machine in SPECIAL mode).
Note: You can run NT4ALL with the /t option to verify that SPECIAL mode is on. Reboot.

The computer will no longer allow ANYONE (including administrators) to log in. The problem does not seem to be reversed no matter how many reboots are attempted.

If attempting to repair the OS with the Windows NT cdrom, the computer will allow for logins, but run VERY slow. (All CPU ticks are taken by SERVICES.EXE and lsass.exe).

4. Possible Solution

Disable write access to the winnt/system32/ directory for all users except the Adminsitrator, until a vendor solution is provided.