Can't add new products, won't manipulate database.
 

For some reason, I haven't been able to add any new products or plugins that manipulate the database. Every time I upload a product/plugin, it says it uploaded fine. But when I go to use it, I get database errors saying that certain tables, fields, etc do not exist. However, products/plugins that just manipulate current data work fine.

I'm currently on 3.54, but this was a problem back when I was on 3.52 (just upgraded tonight hoping that would fix it, it didn't). There have been no permission changes on the database (I'd be the one to have to make them).

I have installed (and these all work):
* Welcome headers - Improve community registration rates
* Who Viewed My Profile
* Moderator Statistics
* How many users registered today
* Miserable Users
* Automatic Welcome PM
* Show Birthday Icon in Postbit
* vB Staff Titles
* Reported post creates new thread.
* Members who have visited the forum (Today or last 24 hours).
* Make Sticky Threads Bold
* Invites System
* Username Management
* Official SigmaChat Integration
* Welcome Panel v1.0
* Randomly positioned ad in between postbits in showthread
* Admin Mass PM Members
* Referrer Statistics
* Show Icon if User has a Profile Picture
* User-Ban Info
* Quick Admin Tools

Unfortunately I can't remember the last one I installed. Any suggestions?

Hmm ... if a product import is successful it shoul work.
If you do get DB errors, try to uninstall that specific product and install it again.
If it still does not work afterwards, we'd need more specific information (eg. which product, which db errors, etc.)