Unit price getting blank in sales line,How to fix

Hi all,

I have an item named as 555555, there is no unit price sell tab. 

I have place an order from project management system.

project--> manage--> item tasks--> sales order 

i have give an line item 555555. enter the value 2000 as unit price at sales line.just i pressed a tab. the price is disappear on the form. How can i fix this.

Please guide me.