SSL-Observatory exception 0x80004005

Sometimes I get this error in the console:

[Exception... "Component returned failure code: 0x80004005 (NS_ERROR_FAILURE) [nsIURI.host]"  nsresult: "0x80004005 (NS_ERROR_FAILURE)"  location: "JS frame :: file:///C:/Users/[redacted

username]/AppData/Roaming/Mozilla/Firefox/Profiles/[redacted profile]/extensions/https-everywhere@eff.org/components/ssl-observatory.js :: SSLObservatory.prototype.submitCertChainForChannel :: line 434"

data: no]

The line in question contains:

this.log(INFO, "SHA-256 hash of cert chain for "+new String(channel.URI.host)+" is "+ chain_hash);

Add-on Version: 3.5.1 Firefox Version: 29.0.1 (German) OS: Win 7 SP1 (64bit German)

I'm unable to reproduce it. I just found them because legacy/trac#12224 (moved) got created and I experience crashes as well. Not as frequent as the reporter mentions.