Please help my gerbil is acting really strange.?

I take my gerbil out 3 times a day for an hour each time. I took him out once this morning and later in the afternoon I changed his bedding. When I went into my room to let him play, I moved his house(hideout) and he was just sitting there, he looked frozen. I took him out and placed him on my floor(in my gerbil-proof room) and he ran right under my computer desk. I thought he had some treats back there from earlier but when he didn't come out I looked under the desk to see him just sitting there, staring. I put my hand under the desk and he started inching away from it, eventually coming out only to run away from me(at this point i was trying to put him back in his tank to let him rest). When ever I tried to scoop him up he would squeak. He looked totally petrified... I finally got him and he jumped from my hands(thankfully he landed in his bedding). I shut off all the lights and closed my door to let him chill out... Please, does anyone know what just happened??? (he was acting fine until I changed his bedding? same brand of bedding and everything)..