histlog file permissions

Hi.

I recently noticed I'm not able to view the history log file via the web
interface. I can see that when it was working the histlog files had
permissions of 644. For some reason they are now written with 640
permissions and xymon is unable to display them. If I manually chmod to 644
xymon can read them. Where can we configure the permissions with which
these files are written? I'm talking about the files at xymon/data/hislogs
by the way. I should also mention that xymon:xymon has ownership of these
files.

Thanks,
Jon.