Error in TOAD (ORACLE developer)

Hi,
I am an Oracle developer and I use TOAD as its sequel developer.
Whenever I try to start TOAD, an error window pops up on the screen.
The screenshot of the error is as under:

Error
Why am I getting this error when my application is working perfectly?
Any suggestions regarding this problem are most welcome.
Looking forward to your replies
Regards
Julie
