7100t v4.0 & Instant messaging v3.8-- Phone became very slow

I bought a new 7100t last week. It had v3.8 software on it and everything was working fine. The instant messaging - yahoo was working great.

I downloaded and installed the v4.0. But since then my instant messaging is not working and my phone has become very very slow. It takes ages to respond to click.

I have even tried the last paragraph instructions given in the installaition manual about deleting the T-Mobile USA IM Client Application & Instant Messaging Application and resintalling on the air.

Please help

Thanks
Prat