[GENERAL] Cause of error message?

An old app is giving a new error message. I query a table and make one update. Later I come back to query the table again and get this error:

 

ERROR: current transaction is aborted, commands ignored until end of transaction block

 

The error only occurs after I have made an update. As long as no updates, I can query multiple times. Can anyone give me an idea of what sort of actions or errors usually cause this error?

 

Thanks,

Bayless