This is most likely due to your User Entry settings (within the Reference Data menu). You probably have multiple roles selected which are causing a system conflict.
Agency Admin will provide you with full access to the entire system. If you are also a Consultant role on the system and have been attached to assignments as a consultant, then it is essential you do not amend your existing User Entry record as this will cause further issues.
If this is the case then we recommend you create a new user entry for yourself with just Agency Admin role attached and leave the original User Entry record with the Consultant role attached. If however you have not been used on the system as a consultant at all then you will be OK to remove all the other roles from your existing user id.
Please note you will need to log out and in again for the changes to take effect.