Blank Categories when Creating or Editing

When I create/edit a category, category details do not get saved. Instead a blank entry is created and in the case of an update, the existing details are removed with blanks. The database in the backend also shows blank values.

What can I do to find out what's going on and why categories are not being saved?

I've updated eshop to the latest version 1.3.1 and still experiencing the same issue.

Just noticed that this seems to be an issue with Eshop in general. I am unable to add products as well. The product name does not get stored.

Hello Ozgur,
The reason of problem because you enabled 2 language system plugins (System - Language Filter and System - Language Code) while your site is not multiple languages. So to solve the problem, please go to Extensions->Language Manager to disable these plugins, then it should work.
Please try and let me know the result.
If it does not still work, please send me the back-end log-in account to your site in the ticket system so I can help.
Sincerely, Giang

I had only "System - Language Filter" enabled. Disabling this resolved the problem. Thanks!

No problem Ozgur,
Don't hesitate to let me know if you need any more helps.
Sincerely, Giang