Interface all but crashes when going to view locations


here are the 2 macs we used so far:
MacBook Pro
17-inch, Early 2011
Processor 2.2 GHz Intel Core i7
Memory 4 GB 1333 MHz DDR3
Graphics AMD Radeon HD 6750M 1024 MB
Software OS X 10.8.5 (12F45)

27-inch, late 2009
Processor 2,8 GHz Intel Core i7
Memory 8 Go 1067 MHz DDR3
Graphics ATI Radeon HD 4850 512 Mo
Software OS X 10.8.5 (12F45)

line:100 Gb optical fibre

when visiting locations others have created, especially those with quite a bit of content like for example Johnnys magic world, the interface all but crashes. it gets totally stuck, often can hardly move around, at times cannot even chat, the avatar or the builds we do see flash randomly like strobes, and we cannot even tp back to the sandbox or home by typing cmd G. It was hard even to do a log out, a times impossible as any action in the viewer as it lags completely. I wonder if this is due to our computers or if it has other reasons, or is there any settings that can be changed.