On 2 different systems with Win7x64 have this bug. Sigil 0.7.1 wont start. First start 0.6.2 to create config files in C:\Documents and Settings\USER\AppData\Local\sigil-ebook\sigil\.., after that sigil 0.7.1 start normal. But after some time (or after restart ) 0.7.1 wont start again. The procedure is the same - delete all files in config dir, start 0.6.2 and after that start again 0.7.1.
I'm not using firewall.
Have another bug in 0.6.2 and 0.7.1. If in clipboard have some info, after closing Sigil this info saved in sigil.ini and file may expand to 10, 20, ...50 MBs. Its confusing.
Thats it. Will see next release.