Please attempt to do the following to speed up the program and fix the issues:
1. Always launch the program as administrator (right-click the Forex Tester icon -> run as administrator).
2. Remove all indicators instances that you do not need at the current moment. 
For example, you may have 2 MA on 2 timeframes (let’s say on M5 and M15) of one chart. Each of these MA instances will be calculated separately, so it is recommended to remove all indicators that you do not need at the current moment and leave the indicators only on the timeframes which you use. In this case our program will need less time to load the project.
3. Check that no automatic strategies are running at this moment, or just turn off strategy execution ("Testing -> Enable/Disable Strategy execution" menu). 
4. Create a new project and use the "Generate ticks by OHLC points" option.
5. Perhaps some of your data files were corrupted. Try to delete the data using the “Clear history” button and then download it from Data Center again.
6. Attempt to decrease the value in the “Tick package size” drop-down menu.

If this doesn’t help then it’s likely that some program files are damaged.
Please download Forex Tester , install it on your computer into another folder (for example, C:\ForexTester3_NEW). Please DO NOT install it into the Program Files folder.
After that, launch Forex Tester 4 as administrator (right-click -> run as administrator) and register it with your key.
If you need to keep your historical data, projects and templates then please do the following:

1. Go to program folder (C:\ForexTester4 by default) and backup these folders: "Data", "Projects", "Templates"
2. After you reinstall Forex Tester, replace the corresponding folders with those that were backed up.