Cannot create the filename file

After having saved a file 6-12 times, I get an annoying error that will not allow me to save the file using the same name I previously used

! Cannot create the {filename} file
Make sure that the path and filename are correct

In order to save my work, I must use a different filename (eg - filename2). The original file cannot be deleted either

The next time I reboot my computer, everything is OK again, and I can delete filename, change filename2 back to filename, and erase filename2

This is very annoying, as I sometimes have 5 different file names for the same file. It also means I have to keep changing the name of the file on my website