We are using HDV 1080i50 format. But we have seen the same problem with DV also.
But, now we have discovered the problem and the solution.
Recently we have added a new Hard disk which was formatted in FAT32(windows format) and because it allows only 4 GB file size we were having problems. Now we have re-formatted this hard drive using the format Mac OS Extended (Journaled) and the problem is resolved.
Anyways, thank you Jerry for your response.