Multiple APNs

While travelling, I use multiple SIM cards on multiple networks on an ultrasn0w unlocked iPhone 3GS. I have found that if I have more than one APN (using unlockit), this confuses the poor iPhone and I have trouble getting on to networks other than the most recent one used. My solution - remove all APNs and start again with the desired network. (This is a bit annoying because landing in another country you are without phone service until you can get to wifi). Often, the last (or second last) APN removal will be met with "removal failed". In my experience, the removal will have gone through, however, despite the warning, and you can then successfully reinstall the desired APN and connect on the network. Interestingly, some networks in Asia need up to 30 minutes to register their 3G or Edge network, so an initial fail will sometime be met with success if left in the phone for a while.