Hi, everyone

I am new to Zen cart.
After I set up categories and clicked New Products, filled all information about the product, then clicked Preview. It looked fine, so I clicked Insert, but a warning message shown:

Warning: An error occurred, please refresh the page and try again.

I refreshed many times and re-inserted products, still had the same warning message.

My system is Windows XP and zencart version is v1.5.4

Anyone can help me out where I made mistakes? Thank you very much!