It all depends on what application created the vcf file. There are a lot of format variations, and GPE Contacts is very picky about what it will accept. You just got lucky.

I'm creating an Excel spreadsheet vcf cleaner to take care of the Yahoo vcf -> GPE problems. I'll post a link when it's done. I'm understanding the character set encoding problem better now - it looks like Yahoo exports genuine UTF-8, but then further encodes the UTF-8 output for HTML compatibility (e.g., the accented character a-acute is E1h in the standard Windows ANSI character set - that becomes two 8-bit characters C3h A1h in UTF-8, but then gets further altered to the 6 characters =C3=A1 in Yahoo's exported vcf file - but GPE Contacts can't read any of these forms without choking).