SQl Server App On Multiple PCs-URGENT

I have a windows-based application that I use to manage fitness events (road races, mountain bike races, etc.). I have the application set up on multiple computers for three reasons:
1) We often manage multiple events on the same day, and
2) I back-up race data during the event in case of catastrophic data loss/hard drive crash/etc.
3) I am trying to set up the possibility of letting race participants sit down and enter their registration data on a laptop to save our staff (generally me) from having to enter several hundred ourselves on the morning of the event.

That is the scenario. Here is the problem: the entire system works very well on our domain/network but when I take the system to a remote site and set up a work-group it is not reliable in the sense that it sometimes works but other times times out.

For instance, lets say a participant sits down at computer 1 and enters their data. The data is sent to sql server on computer 2 via a vb6 windows application. And a registration form is printed out on a computer connected to computer 2 and shared amongst all of the workgroup computers. In some cases it works but generally speaking it times out. Often times if I set the workgroup up at my location it will work but not at a remote location. Several of the computers have wireless capability which I use at home but not at the race site. I connect to the workgroup via cat 5, etc...

The thing that frustrates me is that it works at home but not on the road. Are there any sql server gurus that can point me in the right direction? I REALLY need to get this resolved.

Thanks in advance~