Question: output from dsolve

I have used the dsolve feature and solved a normal ODE. The problem ariss from evaluating that result for different y(x) values. I get the y(x) attached to some message regarding a table. The ODE was y'=-400t*y(t). After solving the diff eq, I evaluated y(t) at t=0 and I got a nice answer, which I defined as t[0]. A few lines later I attempted to use t[0] in a simple subtraction step but got 19.7table[....]... where 19.7 was the correct answer but the subsequent phrase table referred to earlier y(t) evaluation. So, even though t[0] gives a nice answer it can't be used for any calculations. How do I rectify this problem? Does this make any sense to anyone?
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