T200 is an air interface timer regulating the communication between MS and BTS. It defines the rate of repetition of a message (on BTS side) on the air if it is not acknowledged by MS.
If the message was repeated N200 times and no answer was received by MS, an error indication with cause T200 expired is provided to BSC.
Probably there is not a correct setting of T200 or N200 or the DL quality/level is very bad. Another problem could be the use of the same BSIC between adjacent cell, causing some problem during handovers.