I hit the very the same error as Fab while trying to replace JBoss logging with logback 1.0.11 on a JBoss 8.0.0.Alpha1 snapshot version. Unfortunately the exception message is not complete. The last part is missing. The logger to be created is named as follows:
org.jboss.as.clustering.impl.CoreGroupCommunicationService$ViewChangeEventProcessor.AsynchViewChangeHandler

To solve this problem i rewrote method ch.qos.logback.classic.util.LoggerNameUtil.getSeparatorIndexOf() to treat DOT and DOLLAR constants with the same priority. Just replace said method with the following and it will work as expected:

  public static int getSeparatorIndexOf(String name, int fromIndex)
  {
    int dotIndex = name.indexOf(CoreConstants.DOT, fromIndex);
    int dollarIndex = name.indexOf(CoreConstants.DOLLAR, fromIndex);

    if (dotIndex == -1 && dollarIndex == -1) return -1;
    if (dotIndex == -1) return dollarIndex;
    if (dollarIndex == -1) return dotIndex;
    return dotIndex < dollarIndex ? dotIndex : dollarIndex;
  }

The relevant loggers are now created in the expected way:

1. org.jboss.as.clustering.impl
2. org.jboss.as.clustering.impl.CoreGroupCommunicationService
3. org.jboss.as.clustering.impl.CoreGroupCommunicationService$ViewChangeEventProcessor
4. org.jboss.as.clustering.impl.CoreGroupCommunicationService$ViewChangeEventProcessor.AsynchViewChangeHandler