Method may only be called on a Type for which Type.IsGenericParameter is true

I am getting this error on a routine which uses reflection to dump some object properties, something like the code below.

MemberInfo[] members = obj.GetType().GetMembers(BindingFlags.Public | BindingFlags.Instance) ;

foreach (MemberInfo m in members)
{
    PropertyInfo p = m as PropertyInfo;
    if (p != null)
    {
       object po = p.GetValue(obj, null);

       ...
    }
}

The actual error is "Exception has been thrown by the target of an invocation" with an inner exception of "Method may only be called on a Type for which Type.IsGenericParameter is true."

At this stage in the debugger obj appears as

  {Name = "SqlConnection" FullName = "System.Data.SqlClient.SqlConnection"} 

with the type System.RuntimeType

The method m is {System.Reflection.MethodBase DeclaringMethod}

Note that obj is of type System.RuntimeType and members contains 188 items whereas a simple typeof(System.Data.SqlClient.SqlConnection).GetMembers(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance) only returns 65.

I tried checking isGenericParameter on both obj and p.PropertyType, but this seems to be false for most properties including those where p.GetValue works.

So what exactly is a "Type for which Type.IsGenericParameter is true" and more importantly how do I avoid this error without a try/catch?