Opening the Clan Manager frame loads the contents of the stash (assuming you haven't done that already this session).
Which is convenient, but it makes the server request in the thread which deals which handling the GUI.
If that request takes a long time or hangs, the UI will be unresponsive.
I haven't seen that, but I do get this stack trace in my DEBUG log every time I open the clan frame for the first time in a session:

Code:
Runnable in event dispatch thread
class java.lang.Exception: Runnable in event dispatch thread
java.lang.Exception: Runnable in event dispatch thread
	at net.sourceforge.kolmafia.StaticEntity.printStackTrace(StaticEntity.java:387)
	at net.sourceforge.kolmafia.RequestThread.postRequest(RequestThread.java:283)
	at net.sourceforge.kolmafia.RequestThread.postRequest(RequestThread.java:249)
	at net.sourceforge.kolmafia.session.ClanManager.getStash(ClanManager.java:292)
	at net.sourceforge.kolmafia.swingui.ClanManageFrame$WithdrawPanel.<init>(ClanManageFrame.java:388)
	at net.sourceforge.kolmafia.swingui.ClanManageFrame.<init>(ClanManageFrame.java:123)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at net.sourceforge.kolmafia.CreateFrameRunnable.runConstruction(CreateFrameRunnable.java:286)
	at net.sourceforge.kolmafia.CreateFrameRunnable.createFrame(CreateFrameRunnable.java:182)
	at net.sourceforge.kolmafia.CreateFrameRunnable.run(CreateFrameRunnable.java:164)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:301)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Runnable in event dispatch thread