FraGGod

Thanks, Gort. I've verified the files and TC found 30 wrong CRCs, including spells.bif, SFXsound.bif, scripts.bif, MovieCD6.bif and alot of others, but I guess ToSC is the source of it, thanks to Ascension64 for pinpointing the problem. ScuD suggested in PM that my BG distributive is somehow corrupted too.
Strange thing that it always worked, with BG1tutu too, nothing complained, so I've tried to install it all under MS Virtual PC with WinME to the same result... guess its just some rare incompatible version of ToSC then, nothing that a few hours of downloading won't fix anyway)
Thanks again for all the answers and the great mod.

I think there are some problems with your BG/TotSC installation. Try to make a full reinstall of BG1.

Tried it today, no improvements.
Now I think the problem lies in one of the mods I've installed prior to BGT, because last "File Not Found" errors in filemon log seem to be caused by files in override dir, BP forum states that all the mods I've installed should install (and work) correctly in this particular order.
Okaay, lets reinstall BG2 now...)

Edit: Same problem with a clean BG/ToSC & BG2/ToB install. Prehaps someone can generate a list of files from BG1 dir, so I can check that they all present, please?