So, Not that I don't think you have, but the question needs to be asked...
Have you made sure the devices you are trying to use SNMPv1 from have it available?
For instance... Doing something like printing out each device into a log file to see the attempt to pull something simple like sysName or sysUpTime and showing pass/fail or the return value in blocking mode?
This way you could create a baseline or proof that the at the least it works on all the devices you are attempting to gather information from.