Access Point keep droping signal

The signal to an access point that works with handhelds were I work was dropping frequently when a lot of the night-staff were using them at once. So I thought of moving the AP to the other side of the building, mind you that this building is over 100 years old with thick stone walls so figured this would help. I tested everything after the move and handhelds logged on to the server fine. Late that night (this is a comedy club) all the units disconnected and would not reconnect to the server. My question is about the setup. I moved the AP from one network drop to another, when i did this i created a patch cable roughly 30 ft long to connect. could that be the reason for the sudden disconnection? Is this too long of a cable? the original setup( which i did not install) was one network drop was then hubbed to give connection to a POS station and the AP. The only difference now is the long cable i made. Any tips or help would be great.

Thanks