Dysnomia (also referred to as anomic aphasia) is a very annoying problem, especially when you're collaborating on projects. Luckily, many people that know me think I'm "idiosyncratic" and usually aren't put off when I say something like, "I got stuck in traffic because the Oh-no-the-lights-are-out-people were fixing the wires because of a fallen branch." (No joke, that's something I've actually said out loud to other people.)
That being said, I've formulated a few methods that've helped me deal with this issue (besides everyone around me thinking I just say things weird!). I think these things work for me because the cause of this word-fumbling annoyance is transitory / intermittent in nature. (Dysnomia can also be cause by brain damage.)
1. Dysnomia (transient) comes in many forms. Exploiting this knowledge can help you 'jog' your brain.
2. Most of us are highly visual -- for example, the original poster mentioned that when they'd see a clock, they'd know what it is, but they couldn't name it. Next time you experience this problem, close your eyes and listen to the clock, or touch the clock and look away. The different sensory input (i.e. tactile from touch, or audio from sound) can jog your brain when it comes to words.
3. Multilingual tactics. This is really helpful for 'everyday' words (like clock, desk, sponge, etc.) that are really embarrassing to forget (at least for me) because I use them so much. Sometimes you can't think of the word in your 'native' language, but if you try for it in another language (for me, it's French), you mind find the word. This can help you get back to the word you really want to say. I picked French because if I wind up saying that word instead of its English counterpart, people think I'm just being fancy. (i.e. "I like your chien!" People will be like, "Why didn't you just say 'dog'?")
4. Sneaky tactics can help your brain. Sometimes I'll take a piece of my hair and rub it between my fingers. I have no idea why, but this act can actually help me with stuff like this. Similarly, using aromatherapy helps me, too -- unforutnately, I've yet to discover a method of using this in public, as most people consider see anyone sniffing a vial suspicious, no matter how casually you try to do it. Even if you dab the scent on a hankerchief, people will still think you're 'huffing' -- but when I'm home I can use aromatherapy ot help.
5. Simiarly, getting 'something to chew' can help. No, seriously! gum, mint, whatever -- taste, just like touch and sound, can push your brain back into the 'on position' when it's flickering.
But, yes, I can comiserate. I hate this.