For reference, the RFC EU_SCRP_WN32 tries to establish connection from computer where SAPGui is running to port 33<nr> on Application Server. If this port is not allowed by firewall or network configuration, it will timeout as well.
Details can be seen in trace \AppData\Local\SAP\SAP GUI\Traces\dev_eusp as stated by Alper
Timeout = 60 min
ERROR in RFCMgr_accept: not accepted
RFCMgr_handleRfcError: key = RFC_IO5
RFCMgr_handleRfcError: status = CODE=CM_PRODUCT_SPECIFIC_ERROR STATUS=??? DATA=??? ID=95168356
RFCMgr_handleRfcError: message =
CPIC-CALL: 'CMACCP : rc=20
LOCATION CPIC (TCP/IP) on local host
ERROR partner '10.21.77.21:3307' not reached
TIME Fri Jul 18 13:08:32 2014
RELEASE 730
COMPONENT NI (network interface)
VERSION 40
RC -10
MODULE nix
RFCMgr_handleRfcError: intstat = IO HANDLE=1 DRV=EXT LINE=1180 CODE=5
ERROR in main: initing communication with Abap
ERROR in my_exit: exit value = 4