First, check to confirm that the high pressure is indeed coming from the column and not from a plugged line or valve somewhere else in the system (it probably is the column, but best to be sure). Disconnect fitttings starting from the end of the system and moving upstream until the pressure drops.
Assuming the problem is the column, I would next try backwashing the column (reverse the flow direction). Check with the column manufacturer before you do this. Most "standard" columns (5 micron, 150 mm class) can be backwashed, but some of the newer small columns have different frits on the inlet and outlet and can be damaged by reverse-flush. Of course, your column is already dead, so what have you got to lose? If the pressure drops back down, that means that the problem was caused by a plugged frit. Count yourself lucky, return the column to the original flow direction, and consider preventive measures (see below).
If backwashing the column doesn't help, the next step is to carefully open the inlet end of the column. Put the column in a vise when you do this (the heat of your hand can expand the contents and force some of the packing out of the column). At this point, you are not sure whether the pressure problem comes from a plugged frit or from plugged packing. I like to be systematic: first replace the frit (or entire end fitting with some columns), reassemble and test. If the pressure is still high, then I'll go on to the next step. Other people do both steps at once on the theory that the column is already open).
If changing the frit doesn't solve the problem, the next step is to carefully dig out a few mm of packing from the column inlet and replace it with packing from the outlet of an old dead column or (if you have them available) with small glass beads. This involves making a paste with the replacement packing and ACN and then using a spatula to press it into the inlet of your column. You may have to repeat this procedure a couple of times as the new material packs down. I would use the column in the reverse-flow direction after this procedure.
Note that all of this is fairly time-consuming. It may be more cost-effective to simply replace the column and then focus on preventive measures.
Now, how do you keep the problem from recurring? Pressure problems usually come either from particulates in the sample or from precipitation of sample components. Take a look at your samples: if there is any indication of cloudiness, you need to change your sample workup to get rid of it. I don't know what else is in honey, but most proteins will precipitate in ACN/water, as will higher oligosaccharides. You might want to modify your sample workup to remove these before they can get on the column (e.g., add ACN to an aqueous sample and then filter).
If you can't change the workup, then consider using an in-line filter (to catch particles) and/or a guard cartridge (to catch particles and precipitating compounds). Instead of having to do surgery on your column, you just change the filter/cartridge.
A final possibility, if you have stuff precipitating from your sample, is to periodically backflush the column with something that will redissolve the precipitate (I've done this successfully, but it is the least desirable approach in my mind).
Good luck!
