Are you running the report on the same machine? If not, potentially the database drivers are not the same and so it causes a slowdown. I've had that myself with our Progress database and found moving from Merant to Data Direct did wonders.
After that, I would assume it's something to do with the way the database query is being read or the connection priority. I can't answer for that bit though as it will be how Logicity is picking up the settings from the rpt file.
Thanks,
Andrew