Thanks Bane, I posted here:
But had no replies, felt like I’ve just been talking to myself, so good to finally hear from someone 
. My thread details when the problem started occurring (after change of laptop to 64bit Win7 from XP 32bit, installed several times, never loads). Seems to be related to going to 64bit I guess, and something to do with the plugins.
I haven’t tried trashing prefs - though I have had a little success since my last post.
Similar to the thread you just shared, I deleted the Cubase LE Plug-in Set.vst3 after install. This makes Cubase load, so I can use it (seems to skip studio manager and a bunch of other things in start-up), though looks like various plugins (as expected I guess after removing the file!) are now missing.
I only have Cubase LE5 Ver: 5.1.1.120, and no earlier version - so I can use a different plugin set.vst3 file. I did try extracting the plugin set.vst3 file from the patch that fixes the same problem in AI5, from here:
http://www.steinberg.net/en/support/downloads/downloads_cai5.html
but it didn’t work.
Least I can open projects again, but annoying reverb etc is missing. Just hoping one day Steinberg might reply to my support request, seems to me that just need to modify the pluginset file the same as they did for AI5.