Access violation exception in visual studio

[Sotiris Chatzis]

I have made a programm using the mysql++ API for the visual studio 7. The 
code is:

try
{
Query query = con->query();
ostringstream strbuf;

query<<"select * from vsr";

log << "query= " << query.preview() << endl; 


Result res = query.store();

Row row;
Result::iterator i;
for (i = res.begin(); i != res.end(); ++i) {
row = *i;
cout << row.lookup_by_name("vsr_regtime");
}

}
it creates the following error when it reaches the command row.lookup(..):
Unhandled exception at 0x100119a1 in simple1.exe: 0xC0000005: Access 
violation reading location 0x8054a938

Have you any idea where is the problem causing this error?