I had posted the following (with a few differences) on the kde bugs site:
https://bugs.kde.org/show_bug.cgi?id=330356#c7

So far, except for one other person, no one else seems to have had the problem. Am posting here in the hope that someone else has encountered it.
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The panel auto-hide works fine on system start-up. However after sometime it stops working. Not sure what triggers it to stop. Looks like starting up certain applications / adding widgets can trigger it.

Reproducible: Always Steps to Reproduce:
1. Customize the panel by adding a widget or two and application shortcut or two.
2. open up a few application windows.
3. Un-hide the panel by moving mouse to bottom of screen.
4. Attempt to re-hide panel by moving mouse away from left edge of screen.

Actual Results: Panel won't re-hide. Stays visible until system restart. (not sure what can trigger it to hide properly again)
Expected Results: Panel should re-hide.

SYSTEM: AMD64 llano quadcore, 8 GB RAM Linux openSUSE 13.1 Root partition 70 GB. Swap 7.5 GB Default theme (mostly).

08/Feb/2014
It has got worse after a largish online update performed on 08/Feb/2014.
Now the panel remains visible soon after clicking on the openSUSE application launcher.
The location of the panel (left or top) does not seem to play any role.

There have been reports of similar problems on openSUSE 11.x but not on 13 or 13.1. After six months of openSUSE 13, one would think that _someone_ would have encountered this problem.
I have no unusual widgets, just the following:
1.Notes 2.Weather 3.Dropbox (but the problem occurred even before installing dropbox) 4.Clipboard. 5.Volume 6.Device Notifier 7.Bluetooth. 8.Notifications/Network Management. 9.Time/Date 10.Redshift. 11.System Load viewer.
The only other thing which may be not so common is Matlab which sees daily use. In any case problem can occur on system start-up merely by clicking the application launcher.

NOTE: This problem occurred from day 1 of installing openSUSE 13.
So far openSUSE 13.x has been a great experience, except for this silly thing. .

Best Regards
SKM.