This is the error message I was getting on one of my SharePoint sites. I was really lost and ended up creating a new site hooked up to the old content db, after which is was working again. Except for one part of the site which involved getting data from a SQL Server Analysis Server cube.
I wasn’t able to get the login working. Unfortunately, SharePoint gives a rather unclear error message stating
“The connection either timed out or was lost.”. You can solve this error by switching off impersonation, which will pass on your user credentials. But for some reason, turning off impersonation was causing the site to fail in my case, thus causing the “Cannot complete this action. Please try again.” error.
Now the only way to solve this (as far as I know) is enabling impersonation again, but specifying an account to impersonate which also has access to your SSAS cube. I don’t exactly know how this is going to affect other SharePoint stuff, but untill now I didn’t notice any odd behaviour.
Enabling / disabling impersonation is done via IIS manager. Locate your site, open the properties and navigate to the ASP.NET tab. Open the ASP.NET configuration and go to the Application tab. In the bottom section you can enable / disable impersonation and supply account details. Using the application pool identity account you’ve specified is probably the best option, since you’re already using that account to manage the rights your SharePoint app has got. Just remember to add that same account to your SSAS deployment too!
Edit: please check out this post for more details / a better solution.