The IOException error indicates that OptiTools was not able to load a webpage. It automatically retries several times, so you may see several of these errors together. These errors are caused by any of:
1) An incorrect page name due to a 'typo';
2) A page that has been removed but is still linked to;
3) A slow web server that does not respond within the Network Timeout period set on the Command view;
4) A slow, noisy, or intermittent internet connection.

The first two errors are not recoverable so you will see a string of IOExceptions and only limited data for the page. The other two conditions are recoverable, so you will probably see one or more IOExceptions followed by a successful load of the page. The web in general tends to be a pretty "noisy" environment, so these exceptions are not uncommon. But if they become routine then you should consider increasing the Network Timeout.