The solution cannot be removed when a job is scheduled or running.

Open command prompt and enumerate the running deployments by executing this command:
stsadm -o enumsdeployments 

Now, we obtain the jobid and cancel this deployement as follows:
stsadm -o canceldeployment -id 2529c788-971c-46a3-b69f-a2a0a1fcc851
stsadm -o enumdeployments 
stsadm -o canceldeployment -id d9b076f0-ade0-4ea6-a271-2eaeec3fb6d3
remove-spsolution