Hi Irrigate, what version are you using?
I noticed there was a bug report (Corrective Action Request #372E8FSF ) that deals with a similar issue, but it is believed to be fixed as of version 8.2.
Error code 7 for the Serial Port Read VI usually means that there has been a timeout. If you can simplify your application to just the code that is causing the problem, I will try to reproduce it here.
In any case, if this isn't causing you any problems, you should be able to safely ignore the timeout messages by wiring the error cluster output to the "Clear Errors" VI.
Eric V
National Instruments
Applications Engineer
Certified LabVIEW Associate Developer
"I'm a Ramblin' Wreck from Georgia Tech and a helluva (NI Applications) Engineer!"