EMINEM IS NOT HAVING A GOOD WEEK! 1ST HE GET'S ROBBED THEN HE GIVES A LACKLUSTER PERFORMANCE 2 HIS PEER'S & WE'RE NOT EVEN GONNA TALK ABOUT AGREEING 2 BALLS IN HIS FACE!

Eminem is not having a good week.

The Michigan-born rapper had thousands of dollars worth of items stolen from his L.A. hotel room on Sunday night, including a $60K diamond necklace and his personal laptop.

Thankfully, Em's new album, "Relapse," debuted at No. 1 on the Billboard Top 200 Albums chart - selling a whopping 608,000 copies in its first week - so he'll have the funds to recover what he lost.

But he couldn't have been happy about the live concert debut of "DJ Hero" on Monday night in L.A., either. There, the hip-hopper met with tepid reactions following a performance with Jay-Z.

"When Eminem rapped with Jay, the crowd loved it," said one eyewitness. "But when he continued on his own and did songs off his new album, the energy just died. People were pumped to see him, but he wasn't interacting with his fans. His performance was mechanical, without a lot of personality, and people were pretty disappointed."

Said a second partygoer, "After Eminem finished his set, he left the stage and was waiting on the sidelines, hoping that the crowd would cheer so that he'd have to do an encore. Unfortunately for him, that didn't happen - people started to file out before his set was even done, and didn't seem to really care if he came back or not. So he didn't."

Added our insider, "There was no mention of Saturday's MTV Movie Awards [when Sacha Baron Cohen rubbed his crotch in Eminem's face] at all."

And while the rapper didn't seem to be in the best spirits, his fellow celebrity partygoers had a blast. Leonardo DiCaprio, Usher, Tobey Maguire and Ryan Phillippe rocked out in the front row pretending to rap, and pop starlet Rihanna waved her hands in the air and sang along to mentor Jay-Z's entire set.