I found a solution
and I want to share it with you in case you face the same problem.
You can do the following steps as described in the following link:http://www.google.com/support/forum/p/Google+Mobile/thread?tid=08bdd19915d17db9&hl=en
1. Menu > Tools > Setting > Connection > Destination > Option > Manage > New Destination > Destination Name
2. name it Google Map (or anything you like)
3. select a Icon for the same from list
4. Massage will appear "New Destination Google Map added"
5. Now go to the access point which you want to use with Google Map ie WAP Service or GPRS ie if your preferred access point is GPRS and it is located in Internet Setting in "Destination" go there & copy the same in this way -
Option > organise > copy to other destination
Then go to newly created Google Map destination & paste it.
6. Now open Maps
7. Go to option > Tools > Setting > Internet > Network Destination > Google Map
8. Maps will be connected to net now.
Hope this will help.