Help me out here. This has been stuck in my head for days now.
As I recall, the crew of a space ship are in hibernation. A crew member is awoken to relieve a fellow crew mate. However, he discovers evidence of violence and death. He awakens another crew member who is in a relationship with, despite company protocols. Together they try to figure out what occurred.
They discover that the former duty crew recovered a probe/satellite, which had originated from Earth a long time ago. The object has been tampered with, possibly by an alien race. Once infected the victim becomes ultra-violent and attacks everyone in sight.
The pair launch the remaining crew (still in hibernation capsules) to a nearby ship to avoid contamination, where they are awoken with no ill effects.
Both remain crew are infected and start to turn on each other. Only their love prevents them killing one and other.
At some point, they realize that they can't kill the organism only cause it to enter a dormant state by lowering the temperature, which they subsequently do.
It is mooted that aliens sent the probe back towards earth with the intention of killing off life on Earth (Well humans anyway).
The film ends when the lovers decide to pilot their craft into the nearby star, thus ending the threat to humanity from the hostile organism.