Normally I would say, yeah..I fat fingered my password..etc....but that's not the case. That's the user account that I use to log into vCenter, it has all the necessary access but barfs every time I try to get Log Insight Connected to vCenter.
Try a different syntax on your username maybe it doesn't like that format. And you can leave the password off the command and it will prompt for it if you want.
On a different note Log Insight is pretty awesome so far...fills a nice gap.
I'm not sure if you are using SSO and all of that fun stuff but, just from a syntax test you could try the username and password in quotes to check for any invalid chars or remove the domain from the username.
Also test the user/pass via powerCLI or another type of auth interface.
Holy crap..i'm really stumped here. I've tried everything I know to try and it still will not validate the credentials. I'm going to create a new account and give it admin access to vCenter to see if it will work.
EDIT:
Nope..same error..Invalid Credentials....hrmmmmm maybe it's the password it doesn't like with the special character.