There are various possible reasons for this, usually to do with third party internet security software but they may also be associated with Windows TCP/IP or dial-up adapter issues. You may not have problems with other software, but that doesn't mean the problem is being caused by VPOP3.
Utilities → Misc Settings → Network Tweakspage in VPOP3, try changing the following settings one at a time:
The following methods used to be important for Windows 95/98/ME and NT, but are less so with newer versions of Windows.
Utilities → Misc Settingspage in VPOP3 and turn on
POP3 the SMTP Connection.