Multiple users scenario failing in loadrunner controller

Hi,

I am new to loadrunner testing. I have encountered a peculiar scenario.

I created a script in loadrunner 12 vugen (Ajax truclient with FireFox) and is perfectly working fine there.

When I run the script in controller with one user, it is working fine and all the graphs are generated. But, if i increase the number of users, an error is occuring 'target object was not found.    [MsgId: MERR-205177]' . As mentioned in one of the other threads, I increased step timeout and object timeout to almost 10 min for each step in the script. still, I am getting the same error.

Can anybody help me out for the issue?

Thanks,

Anasuya.