SmartFTP.exe process doesn't quit on program exit

After using SmartFTP for a while, performing standard file transfers via regular FTP, sometimes the SmartFTP.exe process will continue running even after I close the program. This problem is a recurring problem that has happened many, many times. Unfortunately, I cannot manage to purposefully reproduce the problem. Here's the system info from the Help -> About menu:

+- System -----------------------------

Microsoft Windows XP Professional 

Service Pack 3 (Build 2600)



CPU Speed		   : 2399 MHz

Total Memory		: 2046 MB

Free Memory		 : 1237 MB



+- SmartFTP ---------------------------

Version			 : 3.0.1023.4

Time Stamp		  : 2008-09-30 01:00:16

Platform			: x86

Id				  : 400084421

Days in use		 : 596



+- Application DLL --------------------

sfFTPLib.dll		: 1.5.14.6

sfFavorites.dll	 : 1.0.19.4

sfFavoritesShellExtension.dll : 1.0.1.14

sfTransferQueue.dll : 1.0.16.4

sfFTPShellExtension.dll : 1.0.14.4

SmartFTPPS.dll	  : 3.0.1023.4



+- Language ---------------------------

SmartFTP.exe		: 3.0.1023.4



+- Internet Explorer ------------------

Version			 : 7.0.5730.11



+- Winsock ----------------------------

Winsock			 : 2.2