In the edit Item window, when you enter a markup percentage of 100% or more, the markup percentage next to the sales price will be blank.
When you click ok and edit the same item, the markup will show.
This issue has been resolved in the latest release for QuickBooks Enterprise Solutions 14.0.
Update to the latest release:
Go to the Update to the Latest Release web page.
IMPORTANT: Make sure your product is selected. If not, click the Change link and select your QuickBooks product.
Select and follow the instructions for one of the update options: