Strand Rendering Problem ?

[eternal art]

I have a problem when rendering a strand in mental ray , is there anyone have the same problem before ?
I've attached an image to explain the problem .

[Hirazi Blue]

Does this happen also, if and when you draw a Render Region in the Camera View?

[eternal art]

I've found the problem .
When i play the time-line and move the emitter manually then render the problem appear , but when i do animate the emitter it's working fine .