Trouble with .dat files. Need tech help...

Hello again.
Recently, my computer has decided that I am not allowed to use .dat files anymore. Any attempt to save, copy, delete or move a .dat file returns me the "Cannot save/copy/delete (file).dat. Access is denied" error.
Access should not in fact be denied, as the files are mine, under my ownership with full control in my documents. I have a feeling some asshole of a security program is blocking my use of .dat files (could be mistaken for system files).
So could anyone help with this?

EDIT: More info. It won't let me save any of the .dat files in the atomicIVAN directory, but in any other IVAN I can do whatever I please with them. This is very strange. I suspect maybe atomicIVAN got virused, or corrupted or something. Now I have 4 copies of it scattered about my computer which I cannot delete due to the "Access Denied" problem. Ignore this. This is no longer true.

do you use any program to edit the .dat files, because i personally use Microsoft Visual C++ 2008 express edition mostly because I had to get it for school but its free and it works well for the dat files and source code. I hope that helps but it might not.

I use notepad. I'll try to use that microsoft visual stuffs. Thanks.

THANK YOU VERY MUCH IANKILL
Not only has this solved my .dat file problem, it has also made the source code MUCH easier to read.
Thank you again and again!
Have 3 pineapples on me