Is the task on this computer? (it's the only active one showing on your account). Because only PPS sieve tasks are listed...
If it is and the task just hidden from those of us who aren't admins...two months is not unreasonable for that CPU, but definitely too long for the GPU.
GFN20's are very large numbers (6.45M digits), and take a long time to complete on older machines. Are you crunching 24/7?
Eating more cheese on Thursdays.