Help! Apache Logs Problem - Access.log stopped running occasionally

Hi all,

I encountered a strange problem that 1 out of 3 sites access.log
stopped occasionally by itself.

Here's the details:
- Running on Windows NT
- Apache 1.3.3
- PHP Version 4.4.0
- 3 sites running on the same apache server.
- 3 separate access logs for each sites
- 1 out of 3 sites access.log occasionally stopped by itself
- 3 sites are sharing the same error.log
- Error found from error.log : Premature end of JPEG file
- Cronolog is running to split the logs daily

Does anyone have any ideas what could be the cause?