GatewayManager: It worked once and then failed

I used the GatawayManager as required and specified http_host, site_start and site_url for each context. At the beginning and adding just site_start and site_url, it failed one day and the next day it worked fine. Then it failed again and I realized I missed to add http_host which I did but it continues to fail to show up the other domnains. It shows the main one only.

Any suggestions?

Theme x3
Apache version 2.2.21
PHP version 5.2.17
MySQL version 5.1.52-cll
Architecture x86_64
Operating system linux

Thanks in advance and best regards,

Alejandro

I'm using ContextRouter - it does the same as GatewayManager without problems!