Today I can't get the fill bookmarklet to work with that browser –
– but that's probably a transient problem. I have seen the misbehaviour before – without Google Chrome, without MacRumors – no matter how many times I log in, the fill bookmarklet responds as if I'm logged out.
LastPass bookmarklets with OmniWeb
Working as expected:
LastPass for Google Chrome
Maybe something in the macrumors.com domain changed, after 9th June, to enable compatibility with LastPass for Google Chrome.
There's the change log, but I don't treat such things as comprehensive.