cannot add variable to Logic Analyzer

hi all.

working on STM32F207IG with MDK compiler V5.06 update 6 build 750.

debugging "release" version with trace enabled.

sAxis[0].lActualVelocity is an int32 public variable.

impossible to trace vartable because of "Cannot add ... to Logic Analyzer" error. 

sorry but i don't understand the reason why debugger can't work.

thanks for cordial help.

davide