This issue appears to only affect Modelsim PE and not Modelsim SE. Open up the sample.do file that was automatically created and locate the first env command:
env /bfm_system/bfm_memory/bfm_memory/slave/slave/read_req_cmd
Each "change" command that follows assumes that you are in the HDL hierarchy of /bfm_system/bfm_memory/bfm_memory/slave/slave/read_req_cmd, but Modelsim PE is not accepting the "env" command.
Prepend each change command with the hierarchical path that "env" tries to setup:
before - change read_cmd(24:31) 2#00000001
after - change /bfm_system/bfm_memory/bfm_memory/slave/slave/read_req_cmd/read_cmd(24:31) 2#0000000
If there is a new "env" command, the "change" commands that follow will have a new hierarchical prefix.