Unable to add or remove product categories

[Studio 42]

Try to add in .htaccess
ExpiresByType application/json "access plus 0 seconds"
Certainly your hoster cache all json, i think that not only Vm have problems, but Joomla do not use many json response.

[GJC Web Design]

BTW - u will probably find on the FE - i.e. in the DB that the changes are being made..  it is just the return select isn't updated

[koaconsulting]

Thanks for your detailed suggestions. 

I was referring to the browser cache... if I empty the browser cache after adding/removing categories then the list IS populated correctly.

I ran the script URL you sent and it loads fine EXCEPT that the "selected" property has two extra backslashes around the word "selected".  Here's the output:

"<option   value=\"8\">Application Processing and Expediting</option><option selected=\\\"selected\\\"  value=\"6\">Books</option><option   value=\"13\"> - American Institute of Architects (AIA©)</option><option   value=\"18\"> - ASTM©</option><option   value=\"11\"> - Gainesville Independent Testing Services (GITS)</option><option   value=\"12\"> - International Code Council (ICC©)</option><option   value=\"16\"> - National Fire Protection Association (NFPA)</option><option   value=\"17\"> - National Roofing Contractors Association NRCA©</option><option   value=\"10\"> - Prometric©</option><option   value=\"9\"> - ProV©</option><option   value=\"15\"> - Sheet Metal Association Contractors of America (SMACNA©)</option><option   value=\"14\"> - Trane©</option><option   value=\"7\">Courses</option>"

Do you think that could be the problem?

[koaconsulting]

Problem Solved!!!  Turns out it was just the server caching the JSON request.  That addition to the .htaccess file fixed things!

Yeah, we do urge our clients to go with a more reputable host but they usually follow their budget and HostGator is a "lesser of evils" I suppose...

Thanks for all your help, it's greatly appreciated!