Wielding a Bastard Sword in 2 hands makes it a martial weapon.
I assume you aren't proficient with those.
On the other hand, wielding a one-handed weapon in two hands (such as a longsword) is possible by RAW without changing it's type.
Now, with specific overriding general it's not possible by RAW
(though i don't think any sane DM would rule it as such)
Edit: Swordsage'd by Curmudgeon, though i think he missed the point