There are a few things that could be causing this issue:
1.Issue with the device's Wi-Fi settings:
SOLUTION: Select the Wi-Fi that you are trying to connect to and tap "Forget." Then reconnect by selecting that network again and entering whatever password may be needed.
2. Router Problems:
SOLUTION: Unplug its power, wait 10 seconds, then plug it back in. Wait 20-30 seconds for the connection to reestablish.
3. Incorrect Date and Time:
SOLUTION:If there is a discrepancy between your phone's date and time and the router's date and time, the connection may not work. Make sure they match.
For more information regarding this issue see: HTC Desire V Troubleshooting