Problems with IRC calculations - update



Hi,
 I have a problem with some TS's and mostly IRC calculations.I have found
 transition
 state with only one imaginary frequency,visualisation shows it could by the
 correct
 TS, but IRC calculations lead in both directions to the same final structures
 with
 the same value of energy.Please help me with some advice or tricks ,that will
 solve
 this problem.Thank you.
 Thank you for your interest and please forgive my short description of the
 problem.
 I am trying to calculate the reaction path of addition of ammines to NCS groups,
 specially addition of dimers.My current calculations are carried out within
 Mopac and Gamess on Am1 level.I have located a quite reasonable TS of
 "jumping " of H from NH3 group - bounded to Carbon atom of NCS group -
 to another NH3 molecule ( NH4 group is forming ).This Ts has only one imaginary
 frequency ( value about - 1268 ), but IRC calculations in both directions lead
 to the same structures with same value of energy - result of irc is that H from
 NH4 group is being transferred to terminal S of NCS group.
 Then I have located Ts of transferring H from NH4 group to S ( again only one
 imaginary frequency ) and again both Irc calculations resulted to the same
 structures - forming of S-H bond.
 I hope this more detailed description will help with the solution of this
 problem.
 Thank You
 Stanley,student
 PF UPJS,
 Kosice,
 Slovakia