I had the same Belkin thingy and didn't experience dropped frames, so I don't think your problem is necessarily intrinsic to your capture device. Like Marc says, there may be some other things to check out before throwing shedloads of cash at the problem. As well as defragging your drives, you may want to ensure that the minimum number of other applications are running while you're capturing.
However, if you're really desperate to spend money, I ended up getting a Canopus ADVC-55 which if you're lucky you can pick up from eBay for around £100 - although new they're only about £130.
Premiere Pro, Encore, Photoshop, Ulead VS6, WXP Pro, Core 2 Duo, 2GB, 2 x 250GB SATA3 drives, 2 x 250GB USB 2 external drive, DVD writer, GeForce 7300 GS 256MB
The biggest fool can ask questions that the wisest man cannot answer...