vanduino:
If I try to upload my sketch to the 4313 by selecting File/Upload Using Programmer, it compiles successfully but then gives me a "BOARD AT COM6 NOT AVAILABLE" error. There is no COM6 on the system, the device manager shows only COM1 and COM2. I have tried powering down and rebooting, but no change, always the mysterious COM6 error.How to get past this?
Sounds like it is a problem with the IDE, not what you are doing.
Until the issue is fixed, the only workaround would be to build the hex file in the IDE, and then upload it manually using avrdude from the command line. Or go back to 1.0.5. Sucks, but it is still a beta release strictly speaking, so I guess you've found what they are looking for -- an issue.
Put in a report and it may get fixed in the next release, if you are lucky.