If the problem is located in:

WAFileLibrary>>fileSelectors
	^ (self class selectors
		select: [ :each | self isFileSelector: each ])
		removeAllFoundIn: self nonFileSelectors;
		yourself

I suggest replacing #removeAllFoundIn: with #copyWithoutAll: (and
remove #yourself)

I did not find other issue after a fast review of #selectors usage in
Seaside2.8.

WATagBrush class>>tag
	^(self selectors includes: #tag) snip...
should better be written
	^(self includesSelector: #tag) snip...

Nicolas

2009/10/30 Nicolas Cellier <nicolas.cellier.aka.nice at gmail.com>:
> See the thread starting at
> http://lists.squeakfoundation.org/pipermail/squeak-dev/2009-October/140239.html
>
> I zealously refactored #selectors also, and that is controversial, see
> thread starting at
> http://lists.squeakfoundation.org/pipermail/squeak-dev/2009-October/140383.html
>
> In the interim put asSet in #selectors or in Seaside.
>
> Anyway, there should be a place where to put release notes, expecially
> when a change might break some compatibility.
>
> Nicolas
>
> 2009/10/30 radoslav hodnicak <rh at 4096.sk>:
>>
>> What's the motivation behind this change? I just traced this as the reason
>> for my seaside image stopping serving its library files, since a method
>> there gets a list of selectors and then tries to remove some of them (which
>> doesn't work for an array).
>>
>> rado
>>
>>
>> On Tue, 20 Oct 2009, commits at source.squeak.org wrote:
>>
>>> Nicolas Cellier uploaded a new version of Kernel to project The Trunk:
>>> http://source.squeak.org/trunk/Kernel-nice.277.mcz
>>>
>>> ==================== Summary ====================
>>>
>>> Name: Kernel-nice.277
>>> Author: nice
>>> Time: 20 October 2009, 11:28:51 am
>>> UUID: d887faef-c132-4cfc-98e2-259162e0cd01
>>> Ancestors: Kernel-nice.276
>>>
>>> remove #keys and let super return an Array rather than an IdentitySet
>>>
>>> =============== Diff against Kernel-nice.276 ===============
>>>
>>> Item was removed:
>>> - ----- Method: MethodDictionary>>keys (in category 'accessing') -----
>>> - keys
>>> -       "Since method all method selectors are symbols it is more
>>> efficient
>>> -       to use an IdentitySet rather than a Set."
>>> -       | aSet |
>>> -       aSet := IdentitySet new: self size.
>>> -       self keysDo: [:key | aSet add: key].
>>> -       ^ aSet!
>>>
>>>
>>
>>
>