It is serious. Its fairly rare, the last time it happened was in the Senate back in 1979, when the killer B's (the ringleaders had names beginning with B) hid out in an apartment to prevent the Senate from taking action on some items they opposed. I don't think it has ever happened in the house.
This was the week that all of the legislative deadlines start to apply, so bills have already begun to die because they had not moved far enough along the process. Generally though, if your bill wasn't out by now, it was probably dead anyway (we meet biennially for 140 days, ending on June 2).
The R's share some of the blame for getting things to this point. They got into power with a majority for the first time since reconstruction. I think this went to their heads a bit and they pushed a lot of their agenda through the house (they have the votes) and refused to take even reasonable amendments from the D's. After being repeatedly rebuffed on even minor issues, I assume they felt this was their only choice. The last minute "gerrymandered" redistricting map sent down from Washington was the final straw.
I'm sure the House members did not make this choice lightly. Their bills are also dying in the process and the retribution has already started on their legislation that was moving toward passage. Once you start something this big, you've got to follow it through; so they will probably stay gone until Friday morning, which will cause some of the big bills they oppose to die.
Gotta love Texas politics, its never boring!
MJV