pgAdmim 1.12 on WinXP SP3 but this issue was observed in previous releases also
When in table view window applied filter and no rows returned (no row matches the filter rull) then it is not possible to fire context menu of the grid and pick up "Remove filter". In order to reload all rows one needs to click Filter icon, go to Filter tab, clear filter rule and close with OK.
This is due to this context menu can be fired only on row
