My O2 dongle seems to connect to my Work VPN only after 10.30pm. I cant understand why it doesnt work during the day, same laptop, same connection settings, same location? Is it possible the provider limits VPN ports or service during the day?
I'm a consultant and had the same problems connecting to a client's VPN via my O2 dongle. Instead of using PPTP to connect to the VPN, try and use the L2TP protocol instead.
If the company doesn't support this ask them if it's possible to enable this as it fixed my problem completely.