Upload index.htm in FrontPage does not work well

[leifoet]

With FrontPage I change(d) the home index of a website (index.htm)

Since yesterday, this suddenly fails (uploading all other files does work).
If I want to upload the modified index.htm, I get the following errormessage

Server error: The server extensions were unable to access the file 'C: \ name \ websiteOld \ .index.htm.tmp "....

I do not find the file ... \ .index.htm.tmp on my computer.

My tempory solution
upload the changed file under a new name for example index_new.htm
and then change back index_new.htm to index.htm and upload again

How can I solve this annoying FrontPage-problem ?