Error when saving copied selection as pattern

I tried to save a copied section as a pattern earlier today, and got an error. I'm running this particular version as a Portable App, so it could be an issue with that...the error I get is:

Error: Procedure execution of file-pat-save failed: Could not open 'F:\GIMPPortable\Data\settings/patterns/mypattern5.pat' for writing: No such file or directory.

I notice there are backslashes and forward slashes in that file directory. Is that the problem, or how should I go about fixing this? Thanks in advance for your help.

Edit: I'm running 2.6.1