Can you please provide the details of your FlashFXP installation.
From the main menu > Help > About
Then from the About dialog click on the Details tab
Click the "Copy to clipboard" button and paste the info in your reply or send it to me via a private message
Also I am not able to reproduce this issue with FlashFXP 5.4.0 (build 3947)
Perhaps the issue is only effecting a specific site field or maybe there is a specific situation required?