Although Minecraft does not publicly use ID's anymore it still uses them internally. You can notice that when you remove a mod, the warnings about missing blocks will have ID's in the logs.
Also, sometimes, when mods get updated, you will also see warnings in the console about assigning new id's to blocks, finding old id's to the same blocks and converting them.
Not sure about this, but HQM might use this ID's internally. Since they store the quests in binary format, I cant know how they really store the block/items information. But... its pretty common for HQM to just crash when some mod updates and gets his ID's changed. When opening the world, HQM will try to convert the saved progress to match the new quests with the new blocks and sometimes it just fails. Regrowth had this problem on the 0.7 upgrade. It would try to convert the saved quest progress for hours until it finally failed and crashed.
Couple weeks ago they(HQM devs) teased us with a new format to store the quests and quest progress using JSON and that would probably soulve this problem since they would be forced to use the block names to identify them but... they havent delivered it yet.
The best Drastic might do is advise to reset the quests progress when updating to 1.0