Question: Error in DEplot

Hi guys,

I'm trying to draw a phase portrait based on a system of differential equations, but executing the DEplot command gives me the response in the title. 

The command I entered is this one :

DEplot(sysdif,[u(t),nu(t)],t=0..50,{[u(0)=0.831,nu(0)=0.7]},linecolor=red,numpoints=1000, thickness=1, u=0.5...1, nu=0.6...1, color=black);

the system of equation is this one :

eqd1 := diff(u(t), t) = u(t)*[-gamma + (rho)/(mu - nu(t)) - delta*u(t) + pii - (tau)/(alpha + epsilon*exp(-beta*((omega-u(t))/(kappa-u(t)))))] ;
eqd2 := diff(nu(t), t) = nu(t)*[(omega-u(t))/(kappa-u(t)) - (tau)/(alpha+epsilon*exp(-beta*((omega-u(t))/(kappa-u(t)))))] ;

the model is calibrated. I understand that maple cannot store a kind of number but even changing the parameters won't help. I've been looking for people with same error message but using solutions provided by forum members don't work. Before getting that error message i did have the one with "vars must be declared as a list ..." so I did :

u:='u' ;

nu:='nu';

but now I have the error  "unable to store  '[HFloat(0.005711776872341132)]' when datatype=float[8]".

Does anybody have an idea of the solution to my problem ?

Thanks for your time,

best regards,

Louis