You used a physics mod online. *headdesk*
Do you have a backup of your DB.bnk? If so, restore from your backup. If not, install Patch 1.67D, which should wipe all physics changes.
For future reference, the two (widely recognized) "rules" of TDUPE are like the first two rules of Fight Club :cheeky: :
1. You don't use physics mods online.
2. You don't use physics mods online.
In general, change the cars' names in ModTools or TDUPE, but leave performance untouched. Everything possible in ModTools 1.12 is online-safe to change, and everything listed on Dredgy's website as being online-safe is safe as well, but don't touch other settings. Premade physics mods are meant for offline use.
For clarification, the reason physics mods don't work online is because of Atari's cheating detection, which kicks you out if you change horsepower, weight, acceleration, or any number of other key statistics. Many other values, though, aren't restricted in this manner.