thumbnails not saving properly

I have been having a problem with photos that I've edited in Photoshop lately. The thumbnails don't save properly, you see only half of them sometimes but the file is ok when you click on them. I've tried running a virus program, I've defragged, I've reinstalled my editing software and nothing seems to work... please help me... I'm operating on windows 8 and I have a Samsung laptop Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 8.1, 64 bit
Processor: Intel(R) Core(TM) i3-3110M CPU @ 2.40GHz, Intel64 Family 6 Model 58 Stepping 9
Processor Count: 4
RAM: 3987 Mb
Graphics Card: Intel(R) HD Graphics 4000, -2038 Mb
Hard Drives: C: Total - 451934 MB, Free - 349327 MB;
Motherboard: SAMSUNG ELECTRONICS CO., LTD., NP350E5C-A03AU
Antivirus: Avira Antivirus, Updated and Enabled