Internal ip address SSG 550M

Hello. 

We have juniper ssg 550 m , with the help of few people around here everything working fine now MIP VIP , trust to untrust and so.

Now we have just a small problem which is bugging us, trying to figure it out but no luck at all. 

We cisco router which is on internal ip 192.168.1.1

Juniper is on 192.168.1.1 by default

Trying to move the internal ip of juniper to 192.168.1.254 so to replace other firewall. 

And here it comes the problem, when we move it to 192.168.1.254 or any other ip automaticaly blocks after few minutes . 

It blocks public ip's and the internet it self, then if we change the ip back to default 192.168.1.1 everything it's fine. 

Any thoughts on what could be the reason, firewall it's check. anti-spam check , deep inspection check, web filter check. 

None of it makes sense at all.

Thank you.