On the Spring premiere of The Hills, Spencer Pratt traveled to Crested Butte, Colorado - unannounced - to try to mend his relationship with Heidi Montag.

It didn't go so well. Heidi said she needed more "space" and bashed Spencer for showing up at all, and acting like it's all about him in their relationship.

That was awhile ago, but judging from their trip to Las Vegas this week, things still aren't entirely patched up between The Hills couple you love to hate.

Sources at various casinos say that not only did they stay in different rooms, they're actually in different hotels altogether. Talk about drama!

Heidi Montag is staying at the Palazzo, while Spencer Pratt has checked into the Hard Rock. Could there be trouble in Speidi-town?

Looks like trouble brewing for Spencer Pratt and Heidi Montag. 

"Yes it is true," a rep confirmed to People magazine. ‘"They are working on their relationship ... They were there filming The Hills."

While in Las Vegas working on the show, the strange couple was spotted arguing for the cameras at the Palazzo's Dos Caminos restaurant.

When The Hills cameras stopped rolling on multiple occasions, Spencer Pratt left the restaurant while Heidi Montag stayed behind, hanging out with famed Los Angeles club promoter and her Hills / real-life boss, Brent Bolthouse.

Interaction was limited between the two. During his downtime, kept clear of Montag, taking in a martial arts fight at the Hard Rock and later having dinner with sister Stephanie Pratt at Wolfgang Puck's CUT Steakhouse.

In other Las Vegas and Hills news, Audrina Patridge will be in Sin City on Friday to host the Pussycat Dolls show at Pure Nightclub.