I would try to go back to the phpBB as your starting point, rather than a forum that's already been converted to vB. Who knows what irregularities happened in the conversion from phpBB to vB.
As for your specific error, I take it that sreefer_smf is the database name. There should have been a table created in there named "membergroups", and if your "prefix" is the default, that would be "smf_". I'm not familiar with the innards of the converters, so I don't know what it's expecting to find within that table.
Does this converter match the SMF version you're converting to? I see that SMF 2 has table membergroups with field group_name, while the older SMF 1 used groupName. There might be a problem there with the converter, or you're using a wrong version. If the converter is hard coded to groupName, it would either have to be patched to work with SMF 2, or you would have to install and convert to SMF 1.1.16, and then upgrade to SMF 2.0.2.
I'll leave it to someone familiar with the converters to discuss this.