integration with infinity limit has problems

[webmasterpdx]

I tried executing the command:
assume(a>0)
...and then I executed the integral again
....and I got one of those cryptic messages, but when I hit enter (again), it gave me the correct answer of 1/a.

What I'm running is actually this (taken from the virtual calculator)...
∫(e^((-a)*x),x,0,∞)
...interesting I just selected the formula and selected edit-copy and pasted it here, and it didn't appear exactly as on the screen, but it does show the integrate symbol.

Here is a screen capture attached below....