Maybe your client is outdated, try to install the new client here.Also download the latest patch here.
After that install your new fresh client and also extract the new patch to the root of InfinityMu folder or You can just update your client by clicking the "Autoupdater" and it will update on its own.
Thats weird, the suggestion I gave you works for me all the time.
Maybe you need help from the higher staff, Try to ask them if they can help you via teamviewer.