The following conditions, in no particular order, are known to cause hind-end weakness in ferrets:
Hypoglycemia (insulinoma)
Cancer (lymphoma)
Aleutian disease virus
Heart disease
Toxin ingestion
Anemia
Discomfort (enlarged spleen, urinary obstruction)
Injury/fractures
Intervertebral disc disease
Thromboembolism
Chordomas
Poor appetite
Proliferative bowel disease
Vomiting
Myeloma
Sepsis (blood-borne infection)
Liver disease
Kidney disease