Sonicwall VPN connection issues

We have an older Sonicwall 2040 Firewall in our small office.  The few users who travel use the Sonicwall VPN client software version 4.6.4 to connect back to our office.  We often have two users who travel together, and we often see problematic and unexplainable problems with the remote users.

Example 1 -  Two of our employees travel to China to work at a customer site for a week.  They both are staying in the same hotel, but in different rooms.  One user can connect just fine to the VPN with no problems using the hotel internet service.  The other user cannot get a VPN established at all...using the hotel wireless or a wired connection in their room.  Both users have the same model laptop.  When they arrive at the customer's business location later that day in China and use the customer's internet service, BOTH of  their VPN connections work fine.  They go back to the hotel and only the one person can use VPN.  

Example 2 - (this just happened yesterday)  Two of our employees are waiting for a flight at the San Jose airport in California and both are using the free Airport wifi.  Both are using almost identical dell laptops and they are sitting right next to each other at the gate.  One user can connect to VPN perfectly fine.  The other user can't connect at all (just says obtaining IP addresss constantly and never connects).  They both get back home last night and they both work fine from their respective homes.

My co-workers are very frustrated about the VPN's "hit or miss" behavior.  I have no idea what to tell them or what I could change with their settings.  It would be one thing if a user never was able to connect at all, but they can connect successfully most of the time.  It's even more frustrating when their co-worker is down the hall in the same hotel room or sitting next to them at the airport and working perfectly fine, when they can't connect.

Any ideas on what I can do short of buying a whole new firewall/vpn solution?