Are radioactive isotopes of silver dangerous?
A glance through the table of the isotopes in the venerable CRC handbook reveals that the longest lived radioactive isotope of Ag is $Ag^{108m}$, made by neutron capture by $Ag^{107}$.  this has a listed half life of "> 5y", but the capture cross section is only $35\pm5$ barns, pretty small for thermal neutrons.  So, it would be really hard to get a lot of radioactive silver.

Next, all isotopes listed decay by $\beta, \beta^{+}$, EC, or IT (electron capture of internal transitions for the metastable nuclei), with decay energies ranging from 93 keV ($Ag^{107m} \rightarrow Ag^{107}$) to 6MeV ($Ag^{116}$).  Those are ionizing radiation, which would increase your probability of getting cancer.

The 'nasty radiation poisoning' things are actually nasty primarily because of being heavy metals, the radiation comes along for the ride, so to speak.  The normal Uranium isotopes are very long lived, so emit very little radiation per unit time.  Polonium, the scary poison of choice in stories and perhaps by the KGB, in contrast, has a short lifetime (138 days for $Po^{210}$), and spews lots of ~5MeV $\alpha$ particles, heavily damaging tissue (much more so than gammas). 

Given the difficulty in making the stuff, assuming you would try $Ag^{108m}$, (small cross sections, can't chemically separate from the stable $Ag^{107}$, etc., your best bet would just be acute heavy metal poisoning from Ag salts (which may or may not be highly toxic). Or, using a silver candlestick to bludgeon the poor victim to death.