SharePoint 2010 Workflow Task cannot be completed

Hello everyone,

I created a simple SPD workflow (SharePoint 2010) with just two lines:

1) Assign a To-do item "Test" to myself

2) Log a message "job's done" to history list

I then ran the workflow which created a task "Test" for myself;

I open the task and click "Complete Task" and the dialog box was closed;

Then in the task list, the "Status" column for the task has been changed to "Completed", but the "% Complete" and the "Outcome" columns remained empty, which are supposed to be "100%" and "Completed".

The workflow does not continue to step 2 (log the message to history list) and the workflow status remains "In Progress".

This problem only happens in some SharePoint sites, it works fine in other sites...

I appreciate any help!