I'm not sure what you mean about the items. Yesterday, I linked several pieces of gear, asking a couple guildies if they thought they were worth holding onto or not. I moved the "junk" into my backpack from the bank, then sold. That's about when I noticed this error message.
The message is strange though, as it doesn't seem to have anything to do with what's in my bags, bank, or anything else. So far these are the times I see it happen:
1) I was clicking on the pet hunter's inventory window, purchasing spades for pet harvesting. Every time I click, I get the message.
2) I hit the "collect" button on my pet's harvesting screen, that message is spammed (instantly I see it 3 times).
3) I am bundling mats.... the bar fills on the bottom of the screen, each time it fills (completing a bundle), I get that message.
4) I am crafting Serenstum... again, each time one is complete, I get that message.
5) I click to use a pot or food, the message is spammed (on my screen 3 times)
6) I talk to my housemaid, when I choose "crafting" to get new pots, I get the message 3 times.
7) I click the icon to get on my mount, I get the message 3 times.

I try to buy anything from a vendor, I get the message 3 times.
I thought maybe there was a problem with my keyboard - I blew it out with canned air. When that didn't work I took it apart and cleaned each key before putting it back together. That did not work either.
I am at a loss as to what to try next.