Unable to search through members on forum - 403 error

[Donttryandkickit]

Hi,
Trying to help a friend with their site, had issues with an old out of date forum so built a new one and after much messing about managed to import the 2000+ members onto the new site. All users from the old site are now able to login and access the new forum, however, if any member uses the search option to find other members they can view page 1 only any attempts to view the other pages or search directly for a member gives the error code 403 forbidden.

I am looking for any help, advice, troubleshooting anyone can share as to what the likely culprits might be

[Illori]

https://wiki.simplemachines.org/smf/Mod_security_-_Having_problems_with_mod_security