This error may occur as a result of abnormal termination of the RExeTris program which has left improper entries in the buffer file (RExeTBuf.ini). If the current contents of the queue are not important then the RExeTBuf.ini file can be deleted from the Windows main directory. If it is necessary to continue computation of the current queue it might be enough to change the following entry in the buffer file:
[Buffer]
RExeTris=off
and then start the RExeTris program.