1. Close thinkorswim 
 
Go to your desktop and locate the thinkorswim/thinkTDA icon 
 Right-click on it and choose Properties 
 In this next window that comes up, click on a button that will either say Find Target or Open File Location (should be the first of three buttons) 
 In the next window, find the folder titled "usergui" and right-click on it and delete it permanently
 Also find and delete any file starting with “cache.” and delete them , too. 
 Then, look for and open a file that contains “VMOptions”; delete everything in the new window that opens and replace it with this:

-Xmx1024m
-Xms1024m
-Dsun.java2d.noddraw=true
-classpath launcher.jar
-Dsun.awt.disableMixing=true
-XX:MaxPermSize=256m
-Dawt.useSystemAAFontSettings=false
-Djava.net.preferIPv4Stack=true
-Dsun.java2d.xrender=True
-XX:-UseConcMarkSweepGC  

2. Shut off your PC (don't Restart, but Shut Down) 
 while your PC is shut down, unplug your modem/router for about 20 seconds and then plug them back in 
 turn your PC back on

3. Once your PC is back on, click on the thinkorswim icon 
 login as normal