6 year old female cat peeing on "new" things?

i have a 6 year old female cat that is peeing on new things we bring into the house.  not everything, but random things:

• a new box of firestarter logs (2 years ago)
• a travel duffle from my inlaws (last year)
• a brand new shag area rug (this year)
• a suitcase borrowed from my inlaws (two months ago)
• a new dog bed (purchased on Sunday, she's peed on it twice already)

her litter is always cleaned, we use scoop litter.  I have bought the spray from the pet store to eliminate odor - used this on my shag rug as it cost me $400 and she wouldn't quit peeing on it.  here's what I don't understand - she loved the area rug, she loved this new dog bed.  she even loves suitcases - you know how cats love to get inside anything, she even lays in the cardboard boxes we bring home from the club stores.  since she loves these things - rolls all over them, lays on them all the time, just like she does with the christmas tree skirt every christmas, but she never pees on that!  i know these new things aren't stressing her out. i don't understand it.

i have had her to the vet to test for uti.  she just said that it is behavior and told me cats are weird that way.  

any suggestions or help would be greatly appreciated.  all of my pets have been from shelters.  when i got this cat, i also took home a 15 year old cat which passed shortly afterwards.  i also have a little dog that i got two years ago from a rescue.  we are not getting rid of her, so i need to try to decipher the issue!  thanks!