Well first of all pine and cedar should not be used for any small animals as they contain phenols which irritate the respiratory system and may cause skin irritation and fur loss. Some may also be allergic to it but it is ntot he main concern anyways as they should be avoided. Just avoid any and all soft wood shavings such as pine, cedar or spruce. I have heard that the pine in the UK is 'safe' but it is actually spruce bedding which although is not as strong as cedar and pine it is still unsafe.

Another thing hamsters should not be let near the dog nor the dog near the hamster. Your hamster should be kept in a room away from the dog. Hamsters stress easily and this huge animal(your dog) could literally stress you hamster to death.

I think what may have happened is that having this new dog added stress to the hamster which allowed his immune system to lower and made it easy for illness to invade. It sounds like some urinary tract problem I would get your hammie to a vet soon.

I hope your hammy is alright. Oh and aspen is safe as it is a hard wood shaving.