Provided you are absolutely CERTAIN you didn't cross any wires during the case switchout, and your solder connections are still intact (check this, as it's very possible a short has developed) - then it sounds to me like you have a Capacitor gone bad.

Capacitors DO carry quite a charge, even if they've been on the shelf for years. I don't recommend the 'shorting' method to try to discharge it - that's a good way to blow it up! Put a piece of electrical tape or duck tape over the leads for insulation, and just handle them carefully.

The number one killer of capacitors, besides improper voltage, is Age - so you may be swapping one dud for another. Once you have it out, take it to Radio Shack, where they can decipher the encoding on it - and match up a fresh replacement of the proper rating.

Note that they're not always successful matching to current stock, and you may have to order the correct piece. So when you tear into it, plan for the possibility of being 'down, awaiting parts' for a few weeks.

The flash tube rarely blows - though it's not impossible, of course. I would switch the capacitor first, since we know there's a problem there - then proceed as needed.

Let us know how it turns out.