Cannot create/add new categories in WordPress 3.5.1 (An error has occurred. Pl.)

When I am within my admin panel, under Posts > Categories, I am unable to ‘create/add’ any categories. The only category that is listed is ‘Uncategorized’, the default category. When I attempt to create a new category, I receive an error “An error has occurred. Please reload the page and try again.”… which is interesting because when I check my database, the category (in which I had just tried to create) was created, and shows within the wp_terms table (with a term_id, name, and slug). However, my newly created category does not show up in my WordPress admin, and therefore I am unable to assign it to any of my posts.

In addition, I cannot create a new category while I am creating a new post either. When I am under Posts > Add New, and I attempt to create a new category, nothing happens, although it does show up in my database, under wp_terms as mentioned before. I have attempted to fix this in numerous ways, with no success. The only time in which I received a different response in my WordPress admin is when I was attempting to replicate this issue in Firefox, with [Enable JavaScript] disabled/un-checked. Then, my WordPress admin displays “Item added” at the top of the page, however, the new category is not listed under the group of categories to the right. The only category that is listed, is still ‘Uncategorized’. However, the category (in which I just tried to create) ‘is’ inserted into wp_terms (as mentioned before), and ‘is not’ available to assign to any of my posts, new or otherwise.

I have been searching and wrestling with this issue for about 4 days now, with no success, and the only information that I could gather was that this issue is very prevalent, across many version of WordPress, and that no one (above WordPress 3.0) has successfully found a solution for it. Frankly, I am very surprised to see that this issue has not been corrected yet. Either way, I am attempting to seek help via this forum, and would appreciate any assistance in regards to this matter. I am running WordPress 3.5.1 (locally), through XAMPP 1.8.1, Apache 2.4.3, PHP 5.4.7, & MySQL 5.5.27.