I have a 2000 Catera Sport and whenever it feels like having a bad day my sport light flashes when I accelerate just after it shifts into thrid. It won't down or up shift. It stays in third. It acts like when I used the snowflake button durring the winter. It's called 3rd gear start. Only it won't come out of it. Anyone have this problem any may know what it is? I don't believe it's a transmission mechanical problem since it drives fine. Maybe a computer. But which one? Can anyone help me?

I had this same problem last week... 2000 Sport

The flashing light is your transmission light - it means get it checked ASAP.

I had mine checked and it turned out my transmission was shot... 69k miles. Thank god for the warranty, it saved me $2500.
I suggest getting your tranny checked out ASAP before it takes a crap on the highway.

Thanks for the advice. Hopefully I won't need a new transmission since unfortunately for me I have no warranty.