Separation anxiety - whenever I'm more than a foot away!

Hi everyone, my little girl's driving me nuts lately, and I can't for the life of me figure out what's up with her. She's really clingy - and I mean REALLY... today, the only time she wasn't screaming a high-pitched scream was when I was sitting on the floor with her on my lap. I couldn't even sit on a chair and have her on the floor next to me... The thing is, though, that she's ok when we're out of the house, and she's ok in bed - she's not waking up overnight, and she naps for a couple of hours without a problem. She's also ok when she's eating (she's always loved her food). Distraction doesn't work, ignoring her when she's screaming and paying her lots of positive attention when she's not doesn't work... It's driving me crazy, I really can't deal with her screaming for much longer. Does anyone have any ideas on what might be causing it, or any ideas for dealing with it? She's 13 months old. Oh yeah, and we took her to the dr the other day, get the results tomorrow of some tests, but she doesn't really seem sick or anything, just clingy.:wall::wall::wall:

DD is a bit the same...I think at around this age they tend to get a bit of separation anxiety, with DD it's also "any other person but mum' anxiety too...lol. She even hates going to DF sometimes and will cry and try to get away from him until she is back in my arms, or clinging onto my leg. Does she have any teeth coming through at the moment? Often that makes them worse.
Hope she improves a bit soon...does she like playing peek-a-boo? Maybe you could hide behind a door or something so she can't see you for just a few seconds but once you start playing then she'll know that you are still there and haven't gone too far away.