What you did was to clear the Read Only attributes for this folder, sub folders and files. In FAT32 this is enough.
But in NTFS file system, you have to check the file permissions along with the ownership also for the folder.
To check the file permissions, right click on your flash folder in My Documents, select Properties - Security Tab.
Here under your username check the file permissions. Do you have full control?
Click on Advanced - Owner tab and press Edit button. Now select your username and put a check mark on Replace owner on subcontainers and objects and press OK button twice to return to the folder Properties dialog box.
Now click Advanced button, and make sure your username has full control permissions. If not click on Change Permissions and remove the tick mark on include inheritable permissions from this object's parent. Click Add button on the opened dialog box. Select your username and press Edit button. In the opened dialog box, put a check mark on Allow at full control, select Apply to this folder, sub folder and files. Keep another check mark on Apply permissons.... in the bottom of the screen and finally press OK button. Now close all the dialog boxes.
This should now allow you to edit any files in the folder.