amie Foxx reportedly got a "beat down" Thursday night at Usher's Pre-Grammy Party and it was by another unidentified star. Actor Damien Dante Wayans was at the party and tweeted: "So b4 u hear it from WORLDSTAR a STAR STUDDED FIGHT just broke out @ the USHER event I'm out.." Sources say the fight happened right in front of the superstar host and record producer Jermaine Dupri. RumorFix has learned exclusively that Usher was singing, "OMG" when someone came up to Foxx, spoke to him for a minute then punched him. We've been told the unidentified attacker is someone Jamie has worked with in the past and may be a record producer. An eyewitness...