Problem: can not add a new attribute

Hi

I've added a mib for an application I wrote to the folder "<appManHome>/working/mibs" and tried to monitor it using the snmpwalk command and it worked just fine. The application manager is on a linux RH 9 and my application is on a sun solaris machine.
First I had a syntax problem. I wrote the oid without the pre dot and without the trailing dot zero (e.g "1.3.6.1.4.1.3" instead of ".1.3.6.1.4.1.3.0") but then I saw that it is working with the machine sysUpTime value so I've tried this syntax on my oid but the object refused to be added. I could solve this problem (maybe) using the mib browser but from some reason it does not work for me. Whenever I hit the mib browser button in the "add attribute" screen I get the "Problem encountered when displaying the page." error message.
What can be the problem ?

Thanks