The Sims 2: Pets

Hi folks, okay so i got pets yesterday, it was the last expansion pack i had to get, Ive beend fiddling around as you do
I adopted a dog from the telephone and then took it with my sim to the pet stop to get a mate for the pooch, all went of with out a hitch,
but then . . for some reason unknown to me I cant take my pets to community lots anymore, when i arrive live mode becomes
unselectable and only build and buy mode are available, i thought the problem might have occured because I used a custom car
, but the i tried with a maxi's car and even walked to the lot and still it gave the same problem, when i turned the testing cheats on, there was an error with the pet,
being very simple minded i have no idea what the error means, any assistance will be greatly appreciated.