Does it make a difference if you right click in the chart and you select 'Reload All Historical Data'? If not, please disconnect your data feed and go to Control Center-->Tools-->Options-->Data-tab, click Repair DB. Restart NinjaTrader and check if the 60 minute chart loads the requested data.
If data is still missing, please exit NinjaTrader and go to C:\-->Users-->*Windows user account*-->Documents-->NinjaTrader 7-->db and delete the cache folder. Start NinjaTrader and check again.
If the issue remains, please send me the log and trace files. Log and trace files can be found at the following locations. Please attach the files in your email.
Documents--> NinjaTrader 7--> Log--> log.20150224 for today. (log.yyyymmdd for any other date)
Documents--> NinjaTrader 7--> Trace--> trace.20150224 for today. (trace.yyyymmdd for any other date)