OpenVPN: Can’t assign requested address

For no clear reason, OpenVPN on Mac with Tunnelblick (any version, had this problem for a few years already) results in these kind of error messages (and refuses to connect):

2013-02-05 17:44:31 write UDPv4: Can't assign requested address (code=49)
2013-02-05 17:44:33 write UDPv4: Can't assign requested address (code=49)

This seems to appear more often when swapping WiFi/IP range (after my Mac goes into sleep). But also happens when connecting to the same WiFi. It doesn’t change anything whether I disconnect OpenVPN before putting the Mac to sleep.

The solution I’ve found to solve this is:

1. Disconnect OpenVPN (via Tunnelblick)
2. Turn off WiFi
3. Run the script I’ve attached below (flush.sh)
4. Fill in your admin/sudo password
5. Hit ctrl+C if it doesn’t exit instantly (happens in 99% of the cases)
6. Run the script once or twice more to be sure, it will exit correctly this time
7. Reconnect to the WiFi
8. Reconnect OpenVPN (via Tunnelblick): this time it will work

The script (name it flush.sh, chmod +x, and run ./flush.sh via Terminal):

Edit: updated script (29/01/2014)

#!/bin/bash
# Change IFACE to match your WiFi interface 
# (en0 on Macbook Air and Retina, en1 on old Macbook Pros with ethernet) 
IFACE=en0
sudo ifconfig $IFACE down
sudo route flush
sudo ifconfig $IFACE up

In case the script hangs (sometimes, route flush hangs): hit ctrl+C, and execute it again.