Comment 1 for bug 423145

Thanks for the report, Pete! This is likely a bug that was half-fixed in duplicity 0.5.18 (which you should have in Alpha 4). The rest of the fix was in 0.6.00 (which will be in Karmic+1). A possible workaround is to run:
ulimit -n 4096
or some such number to make it work.