We got a tip from a reader claiming they and others are having trouble logging in to the official Foursquare client for Windows Phone. The problem reportedly started a few days ago and people on the Zune Marketplace have been giving some poor reviews citing the same issue.

For what it's worth, we just created an account with Foursquare (web) and are unable to login via the client, just like others are reporting. Anyone else having this problem if you logoff the app and log back in? We're reaching out to Foursquare for a comment and will keep you posted...

Comments via WP7Applist; Thanks, Victor Hugo Marques, for the tip