I have the same problem. Do you have many fonts installed? I have 232 fonts listed in Windows composed of about 831 font files (About 602 megabytes total).
I checked the startup of the opera.exe subprocesses using Sysinternals Process Monitor and it looks like every time a new opera.exe process starts it is spending 60 seconds digging around in C:\Windows\Fonts loading in every font file. Stack trace shows the Windows "DirectWrite" system may be involved. Since I had to disable that in Chrome for unrelated reasons (all international characters render as squares) I thought I would try disabling it in Opera. When I disabled "DirectWrite" it dramatically sped up Opera's load times and it seems more responsive as well.
(This worked for me, but I give no guarantees)
Open this url:
And click the "Enable" button (this will actually disable DirectWrite even though it says enable)