Plugin "Xfce4 Timer" unexpectedly left the panel, do you want to restart it?

xfce4 timer plugin in panel properties

I have installed LinuxMint 13 xfce in my friends pc some days ago. I also Install Xfce4 Goodies in this pc. But alas! My bad luck. None of any plugin works perfectly after installation. Look at the image below.

It said:

Plugin "Xfce4 Timer" unexpectedly left the panel, do you want to restart it?

The plugin restarted more than once in the last 60 seconds. If you press Execute the panel will try to restart the plugin otherwise it will be permanently removed from the panel

It has only two options: 1. Execute and 2. Remove

I clicked 'Execute' several times, but same message apear every time. I did not start the plugin once more in last 60 seconds. Though same message displaying its ugly face again and again. At last I have to click on 'Remove'. I found that other plugins such 'Network Monitor', 'System Load Monitor', 'Verve Command Line', 'SmartBookmark', 'Quicklauncher', 'Sensor plugin', 'Mount devices', 'Mail Watcher', 'Generic Monitor', 'Disk Performance Monitor', 'CPU Graph', 'CPU Frequency Monitor' etc are behave in same way. None of them start normally. Each of them 'unexpectedly left the panel'.

In this moment I can not understand the problem, so I can not fix it. Sorry, for this sentence.