Third party insurers

In feb 2009 i was involved in a car crash in which the third party was on the wrong side of the road when he crashed into my veichle. I sustained damage to my knee and broken ribs. I was unable to work until may '09. I attended orthopedic treatment until feb '10 and physiotherapy until march '10. However in december 2009 i a transit van went into the rear of my car whilst staionary at lights. This makes it very complicated. The first insurance company have been thoroughly difficult throughout the whole matter and I have this morning recieved a letter from my solicitor stating that the third party insurer is not in a position to make an offer of compensation until they find out if the second crash which was eight months later had any effect on my injuries. The medical report obtain by my solicitor states that the second crash had no impact on my recovering from the first incident and that neither injury were connected.
Why are they doing this? Is it just a stalling technique to waste more time?