If you can see the pens then TrendX is probably running correctly. The trend area would normally be blank if TrendX was the problem. This suggests that the issue may be with the datalog files. On our systems these sometimes get corrupted and we get the symptoms you have described. If this happens we just have to delete the directory which holds the files and let RSView recreate it on start up. This does, of course, mean you lose all of the data but we run duplicate redundant servers so we still have our trends on at least one machine.