I have everything set to Tahoma size 8.
I confirmed this on my XP machine too but that font is set to: Microsoft Sans-Serif size 8.
Did you try making the window so that it's not full screen, then closing and re-opening it. It only seems to happen when you open the program minimized.
Let me know if you need anything else.
~FlashFXP 4.3.1 (build 1967) [x]Registered
~Win 7 Pro 64-bit SP1
~WinXP Pro 32-bit SP3
~Bitdefender Antivirus Plus 2013 - Antivirus
~Microsoft Security Essentials - Antivirus
~Running Behind NAT/Router [x] Yes - Linksys WRT54GS V2 w/ DD-WRT (Build 13064M)
~Running Firewall [x] Yes - Windows Firewall
~Network: Cable, Comcast
Operating System: Windows 7 x64 Service Pack 1
FlashFXP version: 4.3.1 (build 1967)
Installation type: All User - Common data folder
Program folder [Access: Read / Write]
C:\Program Files (x86)\FlashFXP 4\
Data folder [Access: Read / Write]
Temp folder [Access: Read / Write]