[CentOS] htaccess htpasswd and satellite connections

Yeah, maybe this is a bit on the edge....

I am discovering several issues with users on satellite internet 
connections not being able to authenticate via a htaccess/htpasswd 
system. Some users cannot connect at all, some can connect reliably.. 
and some are hit and miss.. works one day and not the next. Yet those 
same users can log in fine if they switch back to their dialup system.

Has anybody else found this and is there a magic tweak somewhere to help 
this work?

Thanks,
John Hinton