Try the LastPass support forum.
http://forums.lastpass.com/

BTW, Firefox 9 was released a week ago.
http://www.mozilla.com/en-US/firefox/

and the same problem arises in ff 9.01 in exactly them same way

You seem to have narrowed the problem down to Last Pass, which is why I recommended their support form. If they know about an issue with their add-on at eBay, they would know if there is a fix for it. If they aren't aware that their add-on is causing Firefox to crash at eBay, they need to be aware of the problem.

There were some security fixes made for 8.0 that caused a huge number of crashes for many Roboform users upon startup of Firefox 8.0 over the 6 weeks that 8.0 was the current version, Mozilla ended up blocklisting older version of the Roboform add-on - after Roboform released a number of updated add-on versions to fix a variety different issues.

I haven't seen any other postings about problems with Last Pass causing Firefox 8 or 9 to crash. Being that Last Pass and Roboform are similar applications and hook into Firefox in similar ways, it's reasonable to assume that Last Pass may have a similar fault like Roboform had until they fixed it.

I have posted a problem on the lastpass site as well - so I will see if they resolve the issue - and if they do I'll add something to this thread.

thanks

I am using Lastpass 1.80.0 with FF 9.0.1 and Windows XP. I have no problem with eBay. So I don't think there's a conflict there. Please post the latest once you hear from Lastpass Support so other users know what to do in case they have the same problem as yours.

I should have said that i'm using windows 7 - and the problem definitely goes if I disable the last-pass add-in. it is only a problem with e-bay: no other site but it is a consistent repeatable fault.