Does encrypting the same file twice with two different keys present a security risk?

It is safe if the algorithm is not weak. If it was not safe then this would count as a serious break of the algorithm. No such weakness is known for (properly employed) AES. TrueCrypt has good reputation and uses a cryptographer-approved encryption mode.

So, yeah, no worry.

While it's true that it's not a problem for AES as Tom Leek correctly points out, some ciphers, most notably RC4, do have this problem. For RC4 at least, it is especially bad if the two keys differ by only a very small amount (for example, the nonce, which is sometimes concatenated with the key material for stream ciphers like RC4, differs). This is one thing that lead to WEP being cracked so completely.